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AP Stats Final
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The pie chart at the right describes the distribution of state tree types for 50 states.. What can we conclude?
There are 10 states that have described a pine tree as their state tree
The following bar graph gives % of buyers of three brands of trucks who are satisfied... what can we conclude?
There are only small differences in the satisfaction of owners for the three brands
If a distribution is skewed to the right, what?
The mean must be greater than the median
A small company makes custom t-shirts and has 6 employees.. The owner gives himself a $30,000 raise, describe how it changes
The mean increases by $5,000. There is no median change
Rainwater was collected in water collectors at 30 different sites near an industrial complex and the amount of acidity was measurd... which boxplots is a correct represnetation?
cant draw the boxplot, median appears to be 4.5, and Q1 at 3.7, Q3 at 5.6
a sample of 250 high school students were asked if you had $1000 to contribute to a charity organization, what would you do? which of the following conclusions is supported by the table
.the proportion of males who said they would contribute to an environmental organization was higher than the females who said they would to such an organization
mr yates picked up a dozen items in the grocery store with a mean cost of $3.25. then he added an apple pie for 6.50$. what is the new mean cost?
$3.50
a small company estimating its photocopying expenses finds that the mean number of copies made per day is 258 per day with a SD of 24 copies per day. which of the following is a correct interpretation of standard deviation?
on average, the number of copies made each day was about 24 copies away from the mean, 258
the five number summary for scores on a statistics exam is 11,35,61,70, and 79. in all, 380 students took the test. about how many had scores between 35 and 61?
95
the heights of the male and female students in a class are summarize by the following box plot, what can be concluded?
about 25% of the male students are taller than tallest female student
when testing water for chemical impurities, results are often reported as bdl.. the following are measurements taken: 5,7,12,bdl,10,8,bdl,20,6. what conclusion can be made?
the median lead level in the water is 7
the population of the US is aging, though less rapidly than developing countries. at right is a stemplot of the residents aged 65 and over in the 50 states.. what is the percentage for utah?
9.0
the iqr for the distribution of states in the previous question is
1.9
a review of voter registration records in a small town yielded the following table of the number of males and females registered as democrat, republican, or another affiliation. which conclusion is supported by the data?
there is an obvious association between gender and party affiliation
a sample of 99 distances has a mean of 24 feet and median of 24.5 feet. unfortunately, it has just been discovered that maximum value in the distribution has been found out to be 50 instead of 40. what happens to the data if we correct this?
median would remain the same, but mean would increase
at the beginning of the school year, a high school teacher asks every student in her classes to fill out a survey that asks for age, gender, number of years they have lived at their current address, favorite school subject, and whether they plan to go to college. which describes the data?
three categorical variables and two quanitative variables
In order for random variable X to have a geometric distribution, what must happened
The probability of success must be the same for each trial
Probability a certain crate has more than 4 contaminated chickens
.889
The mean and SD of the # of contaminated chickens
Mea is 7.2, SD is 2.24
Which of the following variables is geometric
The # of digits I will read beginning at a randomly selected point
The heights of American men aged 18-24 are approximately Normally distributed with a mean of 68 inches and standard deviation of 2.5 inches. Only about 5% of young men have heights outside the range..
63-73 inches
Use the information in the previous problem. About what percentage of the men are over 70.5 inches tall?
16
For the density curve shown to the right, which statement is true?
The area under the curve is between 0 and 1.
For the density curve in question 3, which statement is true?
The mean is less than the median
The area under the standard Normal curve corresponding to -0.3<z<1.6 is...
0.5631
The 16th percentile of a normally distributed variable has a value of 25, and the 97.5th percentile has a value of 40. Which of the following is the best estimate of the mean and SD?
mean=30, standard deviation=5
The cumulative frequency graph at right shows the distribution of lengths of fingerlings at a fish hatchery.
1.2 cm
Which of the following properties is true for all density curves?
I and II only- They are symmetric, The curve reaches its peak at mean
For the density curve, which statement is true?
The density curve is symmetric
For the density curve in the problem above, which is true?
The mean and median are equal.
Suppose that 16 oz bags of chocolate chip cookies are produced with weights that follow a Normal distribution with mean weight 16.1 oz, SD 0.1 oz. The percent of bags that will contain 16-16.1 oz is
34
For the distribution of cookie bags described above, approximately what percent of the bags will likely be underweight?
16
At right is a cumulative relative frequency graph for 48 racers who finished the 50kn ski race at the olympics. Approximately what proportion of the racers finished the race in more than 2.15 hours?
0.45
In the previous question, the mean finish time is 2.164 hours and the SD is 0.85 hours. The distribution is skewed right. What are the mean, SD, and shape of the distribution of z-scores?
mean=0, SD=1, skewed right
The lifespan of all microwave ovens sold in the US approximately normal with a mean of 9 years and a SD of 2.5 years. What percentages of the ovens last more than 10 years?
34.5%
The mean age of presidents is approximately normal with a mean of 54.6. Obama was 47 at inauguration, which is the 11th percentile. Which of the following is closest to the standard deviation of ages?
6.18
Which of the following is true about all Normal Distributions?
The area underneath the curve is=1.
The density curve shown to the right takes the value 0.5 on the interval 0<x<2 and takes the value 0 everywhere else. What percent of the observations lie between 0.5 and 1.2?
35%
The distribution of the heights of students in a large class is roughly normal. Moreover, the average height is 68 inches, and approximately 95% of the heights are between 62 and 74 inches. SD is equal to
3
From past experience, a music store finds the mean number of CDs sold in a sale is 845, the standard deviation is 15, and a histogram is approximately normal. The manager is willing to accept a 2.5% chance that a CD will be sold out. About how many CDs should the manager order for an upcoming sale?
875
IF your score on a test is at the 60th percentile, you know that your score lies...
between the median and the 3rd quartile.
Other things being equal, larger automobile engines are less fuel-efficient. You are planning an experiment to study the effect of engine size (in liters) on fuel efficiency (in miles per gallon) of sport utility vehicles. In this study,
gas mileage is a response variable, and you expect to find a negative association
In a statistics course, a linear regression equation was computed to predict the final-exam score from the score on the first test. The equation was y=10+0.9x where y is the final-exam score and x is the score on the first test. Carla scored 95 on the first test. What is the predicted value of her score on the final exam?
95.5
In the course described in #2, Bill scored a 90 on the first test and a 93 on the final exam. What is the value of his residual?
2.0
The correlation between the heights of fathers and the heights of their (fully grown) sons is r=0.52. This value was based on both variables being measured in inches. If fathers' heights were measured in feet (12 inches), and sons' heights were measured in furlongs (7920 inches), the correlation between heights and fathers heights of sons would be
unchanged equal to 0.52
All but one of the following statements contains an error. Which statements could be correct?
the correlation between mid-August soil moisture and the per-acre yield tomatoes is r=0.53
A least squares regression line for predicting weights of basketball players on the basis of their heights produced the residual plot below
the curved pattern in the residual plot suggests that the linear model is not appropriate
A community college announces that the correlation between college entrance exam grades and scholastic achievement was found to be -1.08. On the basis of this you would tell the college that
the college should hire a new statistician
An agricultural economist says that the correlation between corn prices and soybean prices is r=0.7. This means that
when corn prices are above average, soybean prices also tend to be above average
Which of the following are true statements?
II and III only
There is an approximate linear relationship between the height of females and their age (from 5 to 18 years) described by height = 50.3+6.01 (age) where height is measured in centimeters and age in years. Which of the following is not correct?
the estimated slope os 6.1, which implies that the female children between the ages of 5 and 18 increase in height by 6.1 for each year they grow older
You are interested in predicting the cost of heating houses on the basis of how many rooms the house has. A scatterplot of 25 houses reveals a strong linear relationship between these variables, so you calculate a least-squares regression line. "Lease-squares" refers to
Minimizing the su of the squares of the residuals
Which of the following is true?
a (I forgot to write down the actual answer...sry)
If bivariate data set A has correlation r=0.95, and a second bivariate data set B has correlation r=-0.95, then
you can't tell whether either data set is best described by a linear model until you examine the scatterplots
A regression of the amount of calories in a serving of breakfast cereal vs. the amount of fat gave the following results: Predicted calories= 97.1053+9.6525(fat). Which of the following is false?
If one cereal has 140 calories and 5g of fat. Its residual is 5 calories
A copy machine dealy has data on the number of cop machines x at each of 89 customer locations and the number of service calls in a month at each location. Summary calculations give x=84, sx=2.1, y=14.2, sy=3.8, and v=0.86. What is the slope of the least=squares regression line of number of service calls on number of copies?
1.56
In the setting of the previous problem, about what percent of the variation in the number of service calls is explained by the linear relation between number of service calls and number of machines?
74%
A study examined the relationship between the sepal length and sepal width for 12 varieties of an exotic tropical plant. Varieties X and O are represented by xs and os, respectively, in the following scatterplot. Which of the following statements is true?
Considering each variety separately, there is a negative correlation between sepal length and width
Which of the following statements about the circled point is true?
Removing this student's data point would decrease the slope of the least-squares line
The circles point represents a roller coaster in the Philippines whose maximum height is 70 feet. The observed speed of this roller coaster is closest t0:
55 m/h
Which of the following best describes what s=10/5371 represents in this setting?
The standard deviation of the residuals- observed height minus predicted height
Use scenario 4-1. The intended population for the survey is
all residents of Lafayette
Use scenario 4-1. The response asks you to comment on their survey of local opinion. You say:
This is a convenience sample. It will almost certainly overestimate the level of support among all Lafayette residents.
A candidate for mayor of Dallas wants to know what proportion of city residents support his candidacy. His staff calls 1000 people chose at random from the city telephone directory: 850 of them respond. What are the population and the sample in this example?
Population: all Dallas residents. Sample: the 850 people who respond
A poll conducted by the student newspaper asked, " Who do you believe will win the Ohio State Undergraduate Student Government elections?" In order to vote, one had to access the students newspapers Web site and record one's vote. The results of the poll were summarized in a graphic similar to the following. Which of the following statements is true about these results
The result of the survey are reliable because response to the survey were voluntary
A marketing research firm wishes to determine if the adult men in Laramire, Wyoming would be interested in a new upscale men's clothing store. From a list of all residential address in Laramie, the firm selects a simple random sample of 100 and mails a brief questionnair to each. The chance that all 100 homes in a particular neighborhood in Laramie and up being the sample of residential address selected
The same as for any other set of 100 residential addresses
Scenario 4-3 is a sample size of three from an employee list of a small company. Use scenario 4-3. The simple random sample
Bechhofer, Taylor, Weiss
Use scenario 4-3. Which of the following estaments is true?
If we use another list of random digits to select the sample. the result obtained with the list actually used would be just as likely to be selected as any other set of there names
Scenario 4-4. You want to take an srs of 50 of the 810 students who live in a dormitory on campus....etc. Use Scenario 4-4. The first three students in your sample have labels
4oo, 769, 335
A public opinion poll Ohio wants to determine whether or not registered voters in the state approve of a measure to ban smoking in all public area. They selected a simple random sample of fifty registered voters form each county in the state and ask whether they appear or disapprove of the measure. This is an example of a
cluster sample
A marine biologist wants to estimate the mean size of the banacle semibalanus balnoides on a stretch of rocky shoreline. To do so, he randomly selected twenty 10 cm square plots and measured the size of every barnacle in each plot. This is an example of
cluster sampling
A local tax reform group polls. The residents of the school district and asks the questions, " Do you think the school board should stop spending taxpayers money on nonessential art programs in elementary school?" The results of that poll are likely to
underestimate support for art programs because the way the question is worded
Frequently telephone poll takers call near dinner time between 6 pm and 7 pm because most people are at home then. This is a effort to avoid
nonresponse
The Bradley effect is a theory proposed to explain observed discrepancy between voter opinion polls and election outcomes to some elections where a while candidate and a nonwhite candidate run against each other. The theory proposes that some voters tend to tell pollsters that they are undecided or likely to vote for a non white candidate and yet on election day vote for a white apponet. This is an example of
bias resulting from questioning wording
Use scenario 4-5. This is a(n)
observational study? (i think this is right)
The most important advantage of experiments over observational students is that
experiment can give better evidence of causation
Use scenario 4-7 The farmer has conducted a(n)
experiments, but not completely randomized experiments
Use scenario 4-7 The brand of pellet is
the explanatory variable
Use scenario 4-7. The feed they get is not the only factor affecting the rate at which pigs gain weight. Genetic differences also affect weight gain. It is likely that pigs in litter A are genetically different from the pigs in litter B since the two litters have different mothers. The farmer is only interested in determining which brand of pellets is better, the study suffers from
confounding
An experiment was conducted by some students to explore the nature of the relationship between a persons heart rate and the frequency at which that person stepped up and down on steps of various heights. Three rates of stepping and two different step heights were used. A subject performed the activity for three minutes. Heart rate has then measured at the end of this period. The variables, "stepping rates" and "step height" are the
factors
The owner of a chain of supermarkets notices that there is a positive correlation between the sales of beer and the sales of ice cream over the course of the previous year. During seasons when sales of beer were above average, sales of ice cream also tended to be above average. Likewise during season when sales of beer were below average, sales of ice cream also tended to be below average. What if the following would be a valid conclusion from these facts?
It is likely that the sales of both beer and ice cream are confounded with the another variable, such as a seasonal variation in temp
The principle reason for the use of random assignments in designing experiments is that it
creates approximately equal groups for comparison
One hundred volunteers who suffer from severe depression are available for a study. fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks, in order to determine if there has been substantial improvement in the severity of the depression. The study would be double blind if
neither the volunteers nor the psychiatrist knew which treatment any person had received
Twelve people who suffer from a chronic fatigue syndrome volunteer to take part in an experiment to see if shark fin extract will increase ones energy level. Eight of the volunteers are men, and four are women. Half of the volunteers are to be given shakr fin extract twice a day, and the other half are to be given a palcebo twice a day. We wish to make sure that four men and two women are assign to each of the treatments, so we decided to use a block and the women the other. A block design is appropriate in this experiment if
all of the above
Are dogs better at tracking the movement of white objects? Fifteen experiments of disk dogs who have been trained to catch flying disks in mid air are given the chance to catch a bright red disk or a plan a white disk. Each disk is thrown 1o times for each dog, with the sequqence of disks caught to the proportion of white disks caught compared for each dog. This is an example of a
completely randomized design
A far coin is tossed four times, and each time the coin lands heads up. If the coin is then tossed 1996 more times, how many heads are most likely to appear in these 1996 additional tosses?
998
A randomly selected student is asked to respond Yes, No, or Maybe to the question "Do you intend to vote in the next presidential election?" The sample space is {Yes, No, Maybe}. Which of the following represents a legit assignment of the probabilities for this sample space?
.4, .4, .2
A die is loaded so that the number 6 comes up three times as often as any other number, what is the probability of rolling a 1 or a 6
1/2
You draw two marbles at random from a jar that has 20 red marbles and 30 black marbles without replacement. What is the probability that both marbles are red?
.1551
An event A will occur with probability .5. An event B will occur with the probability .6. The probability that both A & B will occur is .1. What is the conditional probability of A, given B?
1/6
An event A will occur with probability .5. An event B will occur with the probability .6. The probability that both A & B will occur is .1. We may conclude that..
either A or B always occurs
People with type O-neg blood are universal donors. That is, any patient can receive a transfusion of O-neg blood. Only 7.2% of the American population has O-neg blood. If 10 people appear at random to give blood, what is the probability that at least 1 of them is a universal donor?
.526
Of people who died in the US in a recent year, 86% were white, 12% were black, and 2% were Asian. Diabetes caused 2.8% of deaths among whites, 4.4% among blacks, and 3.5% among Asians. The probability that a randomly chosen death was due to diabetes is
.030
In your top dresser drawer are 6 blue socks and 10 grey socks, unpaired and mixed up. One dark morning you pull two socks from the drawer (without replacement). What is the probability that the two socks match?
.500
You play tennis regularly with a friend and from pas experience you believe that the outcome of each match is independent. For any given match you have a probability of .6 of winning. The probability that you win the next two matches is
.36
The security system in a house has two units that set off an alarm when motion is detected. Neither one is entirely reliable, but one or both always go off when there is motion anywhere in the house. Suppose that for motion in a certain location, the probability that detector A goes off and detector B does not go off is .25, and the probability that A does not go off is .35. What is the probability that B goes off?
.75
There are 10 red marbles and 8 green in a jar. If you take 3 marbles from the jar (without replacement), the probability that they are all red is
.147
Jun and Deron are applying for summer jobs at a local restaurant. After interviewing them, the restaurant owner says, "The probability that I hire Jun is .7 and the probability that I hire Deron is .4. The probability that I hire at least one of you is .9." What is the probability that both Jun and Deron get hired?
.2
Select a random integer from -100 and 100. Which of the following pairs of events are mutually exclusive (disjoint)?
A: the number is above 50; B: the number is less than 20
A recent survey asked 100 randomly selected adult Americans if they thought that women should be allowed to go into combat. Here are the results (table). The probability of a "yes" answer, given that the person was female is
.32
A recent survey asked 100 randomly selected adult Americans if they thought that women should be allowed to go into combat. Here are the results (table). The probability that a randomly selected subject in the study is Male or answered "no" is:
.84
Experience has shown that a certain lie detector will show a positive reading (indicates a lie) 10% of the time when a person is telling the trust and 95% of time when a person is lying. Suppose that a random sample of 5 suspects is subjected to a lie detector test regarding a recent on-person crime. Then the probability of observing no positive readings if all suspects plead innocent and are telling the truth is
.591
If P(A)= .24 and P(B)= .52 and A and B are independent, what is P(AorB)?
.6352
The two way table gives info on the performers in the New York Orchestra, categorized by section and gender. You select one musician from this group at random. What is the probability that this person plays a woodwind?
.159
The two way table gives info on the performers in the New York Orchestra, categorized by section and gender. You select one musician from this group at random. If the person is a male, what is the probability that he plays a woodwind?
.182
The two way table gives info on the performers in the New York Orchestra, categorized by section and gender. You select one musician from this group at random. Which of the following statements is true about the events "Plays a woodwind" and is "Male"?
The events are not mutually exclusive, nor are they independent.
In the town of Tower Hill, the number of cell phones in a household is a random variable W with the following distribution:.... The probability that a randomly-selected household has atleast two cell phones is
0.80
A random variable Y has the following distribution:... The value of the constant C is:
0.10
A rock concert producer has scheduled an outdoor concert. If it is warm that day she expects to make a $20,000 dollar profit. If it is cool that day, she expects to make a $5,000 profit..... What is the producer's expected profit?
$11,450
Roll one 10-sided die 12 times. The probability of getting exactly 4 eights in those 12 rolls is given by
(12 / 4) x (1 / 10)^4 x (9 / 10)^8
A randomly chosen subject arrives for a study of exercise and fitness and begins walking on a treadmill at a brisk pace. Which of the random variables described below is discrete?
You measure the maximum heart rate in beats per minute
Let the random variable x represent the profit made on a randomly selected day by a certain store. Assume that x is Normal with mean $360 and standard deviation $50. What is P(X > $400)?
0.2119
You select 40 cards from a standard deck of 52 cards. Let Y be the number of red cards (hearts or diamonds) in the 40 cards selected. Which of the following best describes this setting?
Y has a binomial distribution with n=40 observations and probability of success p=0.5, provided that after selecting a card it is replaced in the deck and the deck is shuffled will before the next card is selected.
In a large population of college students, 20% of the students have experienced feelings of math anxiety. If you take a random sample of 10 students from this population, the mean and standard deviation of the number of students in the sample who have experienced math anxiety is:
mean = 2 ; StD = 1.265
A vending machine operator has determined that the number of candy bars sold per week by a certain machine is a random variable with mean 125 and StD 7. His profit on each bar sold is $0.25, and it costs him $5.00 per week to maintain the machine and rent the space for it. What are the mean and standard deviation for Y = the profit he earns from this machine in a randomly selected week?
mean = 26.25, StD $1.75
Jen's commute to work requires that she take the blue subway line, then transfer to the red line. The length of the trip on the blue line has a mean of 18 miniutes with a standard deviation of 2 minutes..... What are the mean and standard deviation of her entire commute?
mean = 40 mins, StD = 5.48 mins
(Table showing numbers and shit)
The probability that the insurance company will have to pay a claim of atleast $1000 for a randomly selected car is:
0.40
(Same table of numbers and shit)
The expected values of C is:
$2770
(Same table of numbers and shit)
Which of the following is the best interpretation of expected value? (In the choices below, "exp (c)" represents expected value you found in 12).
If the company insures a large number of these cars, they can expect the cost per car to average approximately Exp(c)
If A=result of a single roll of a six-sided die and B=result of a single roll of an 8-sided die, then mean(a) = 3.5, StD(a) = 1.71, mean(b) = 4.5, StD(b)= 2.29. If D=the difference B-A, then which of the following is true?
Mean(d) = 1, StD(d) = Squareroot(1.71^2 + 2.29^2)
Let the random variable X represent the amount of money Dan makes doing lawn care in a randomly selected week in the summer. Assume that X is normal with mean $240 and Standard deviation $60. The probability is approximately 0.6 that, in a randomly selected week, Dan will make less than
$255.
Let the random variable X represent the weight of male black bears before they begin hibernation. Research has shown that X is approximately Normally distributed with a mean of 250 pounds and a standard deviation of 50 pounds. What is p( X > 325 pounds)?
0.0668
In order for the random variable X to have a geometric distribution, which one of the following conditions must X satisfy?
The probability of success has to be the same for each trial.
(It has been estimated that about 30% of frozen chickens...)
The probability that a certain crate has more than 4 contaminated chickens is
0.8889
(It has been estimated that about 30% of frozen chickens...)
The mean and standard deviation of the number of contaminated chickens in a crate are
mean = 7.2 , StD= 2.24
Which of the following random variables is geometric?
The number of digits I will read beginning at a randomly selected starting point in a table of random digits until I find a 7.
In a study of the effects of acid rain, a random sample of 100 trees from a particular forest is examined. 40% of trees show some sign of damage. Which of the following statements is correct?
40% is a statistic
the sampling distribution of a statistic is...
the distribution of values taken by a statistic in all possible samples of the sample sample size from a population
a statistic is said to be unbiased if...
the mean of its sampling distribution is equal to the true value of the parameter being estimated
A survey asks a simple random sample of 500 adults in Ohio if they support an increase in the state sales tax from 5% to 6% with the additional revenue going to education. Let p denote the proportion in the sample who say they support the increase. What is the probability that less than half the sample will say they support the increase?
P(z < 0.5 - 0.53 / square root (0.53)(0.47) over 500 )
you take a simple random sample of size 25 from a very large population in which the proportion is p=0.1, this violates the condition that np>10
mean=0.1, the distribution is not approx. normal
the number of hours a light bulb burns before failing varies from bulb to bulb. the distribution of burnout times is strongly skewed to the right. the clt says that...
the mean burnout time for a larger # of bulbs has a distribution that is close to normal
You take an SRS of size 500 from the 37000 students at Purdue university and measure individuals heights. You then take an SRS of size 500 from the 4,000,000 adults in the state of Indiana and measure their heights. Assuming the SD of individuals heights in the two populations is the same, the standard deviation of the sampling distribution of mean heights for the Indiana sample is...
approx. the same as Purdue sample because both are sample size of 500
a student investigating study habits asks a simple random sample of 16 students in her (large) high school how many minutes they spent on their english... Which of the following best describes what we know about the sampling distribution of means for the student's sample?
mean=45, sd=3.75, shape of distribution is unknown
olive weights are classified according to a unique set of adjectives implying great sizes for example , the mean weight of olives classified ¨colossal"is 7.7 grams.. suppose a particular company's crop of "colossal" olives is approximately Normally distributed with a mean of 7.7 gm and a standard deviation of 0.2gm. Which of the following represents the probability that the mean weight of a random sample of 3 olives from this population is greater than 8?
P(z > 8-7.7 / 0.2 over square root 2)
in a large population 46% of the households own DVD records. A simple random sample of 100 households from this population is to be contracted...
P( z > 0.5-0.4 / square root (.46)(.54) over 100)
the chipmunk population in a certain area is known to have a mean weight of 84 g and a sd of 18 g. a wildlife biologist ... Which of the following best describes what we know about the sampling distribution of means for the biologists sample? [Assume the 9 chipmunks represent a SRS of chipmunks in the area]
mean=84, sd=6, shape of distribution of unknown
suppose you take a random sample of size 25 from a population with mean of 120 and a sd of 15. your sample has a mean of 155...
the sampling distribution of the sample mean
in order to use the formula sd= sd/squareroot n to calculate the sd of the sampling distribution of the sample mean, which of the following conditions:
1. n >/= 30
2. the populations distribution appears normal
3. the sample size is less that 10% of population size
3. only, the sample size is less that 10% pop. size
suppose we wish to estimate the percentage of students who smoke cigarettes at each of several colleges and universities. two of the colleges are Wabash college and Purdue university. what should the relative size of our samples from each school be if we want the sampling distributions to have approx. the same sd?
we should take the same size samples from each school
a census of the labor force of a large metropolitan area found that the time it takes people to commute to work has a mean of 20.5 min and a sd of 15.4 min. which represents that probability that a sample of 40 has a mean greater than 25 minutes
p (z > 25 - 20.5 / 15.4 over sq r 40)
suppose you are sampling from a distribution that is strongly skewed left. which of the following statements is true
as the sample size increases, the shape of the sampling size gets closer and closer to normal distribution
which of the following statements are true when taking an SRS:
1. the sampling distribution of x bar has a sd of sd/ sq r n even if not normally distributed
2. the sampling distribution of x bar is normal if population is normally distributed
3. when n is large, sampling distribution of x bar is approx. normal even if pop. isnt
1,2,3 all of these statements are true
in a large population of adults, the mean IQ is 112 with a sd of 20. suppose 200 adults are randomly selected for a market research campaign. the sampling distribution of the sample mean IQ is
approx. normal, mean 112, sd 1.414
according to the Dupont 2012 global automotive report, 25% of all cars manufactured in 2012 were white. in a random sample of 100 cars parked at Philadelphia international airport, 19% of the cars were white. which of the following statements is true
23% is a parameter, 19% is a statistic
the best statistic for estimating a parameter has which of the following characteristics?
low bias, low variability
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