ap statistics midterm review

The probability of having a certain disease is 0.5. The probability of testing positive if you have the disease is .98; the probability of testing positive is you do not have the disease is .10. What is the probability that you have the disease if you test positive?

34%

High school textbooks don't last forever. The lifespan of all high school statistics textbooks is approximately Normally distributed with a mean of 9 years and a standard deviation of 2.5 years. What percentage of the books last more than 10 years?

34.5%

In the year 2016. The mean age of the 12 member of the mathematics department attending the faculty meeting is 37. The 13th member, Mr. Smith, who is 50, got lost and arrived late. What is the average of all 13 members?

38

The number of customers served per day by a large department store is approximately normal distributed, with a mean of 3250 customers and a standard deviation pf 320. Find the range of customers served on the middle 50 percent of days.

(3035, 3464)

An athlete suspected of using steroids is given two tests that operate independently of each other. Test A has a probability of 0.9 of being positive if steroids have been used. Test B has probability of 0.8 of being positive is steroids have been used. What is the probability that neither test is positive if steroids have been used?

0.02

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?

0.1551

Jackie and Devin are applying for summer jobs at a local grocery store. After interviewing them, the store manager says, "The probability that I hire Jackie is 0.7, and the probability that I hire Devin is 0.4. The probability that I hire at least one of you is 0.9." What is the probability that both Jackie and Devin are hired?

0.2

A factory dumps an average of 2.43 tons of pollutants into a river every week. If the standard deviation is 0.88 tons, what is the probability that in a week more than 3 tons are dumped? Assume that the factory's pollution levels are Normally distributed.

0.2578

You play tennis regularly with a friend, and from past experience, you believe that the outcome of each match is independent. For any given match you have probability of 0.6 of winning. The probability that you win the next two matches is ___________.

0.36

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}. What represents a legitimate assignment of probabilities for this sample space?

0.4, 0.4, 0.2

If you buy on ticket in the Liberty Lottery, then the probability that you will win a prize is 0.11. Given the nature of lotteries, the probability of winning is independent from month to month. If you buy one ticket each month for five months, what is the probability that you will win at least one prize?

0.44

You want to estimate the probability that the player makes 4 or more of 10 shots. You estimate 10 shots 25 times and get the following numbers of hits. 5 7 5 4 1 5 3 4 3 4 5 3 4 2 6 3 4 1 7 4 5 5 6 0 7

0.68

The proportion of observations from a standard Normal distribution with values larger than -0.75 is __________.

0.7734

The proportion of observations from a standard Normal distribution with values less than 1.15 is ___________.

0.8749

At Lakeville South High School, 60% of students have high-speed internet access, 30% have a mobile computing device, and 20% have both. The proportion of students that have neither high-speed internet access nor a mobile computing device is _____________.

30%

The average yearly snowfall in Appleton is Normally distributed with a mean of 55 inches. If the snowfall in Appleton exceeds 60 inches in 15% of the years, what is the standard deviation?

4.83 inches

The average number of calories in Yum-Yum Good candy bars is 210, with a standard deviation of 10. If the number of calories per candy bar is approximately distributed, what percent of candy bars contain more than 225 calories?

6.8%

150 students had heights that were roughly normally distributed with a mean of 65 inches and a standard deviation of 2.5 inches. Approximately 102 students would be contained in what intervals?

62.5" to 67.5"

The five-number summary for scores on a statistics exam is 11, 35, 61, 70, 79. In all, 380 students took the test. About how many had scores between 35 and 61?

95

A fair coin is tossed four times, and teach 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

Which of the following are false statements about stem-and-leaf plots? I. They can be used to display both categorical and numerical variables. II. They are useful for both small and large data sets. III. One can easily see the shape of the distribution and unusual data values.

I and II

Which of the following statements are true? I. The area under a Normal curve is always 1, regardless of the mean and standard deviation. II. The mean is always equal to the median for an Normal distribution. III. The interquartile range for any Normal curve extends from μ − σ to μ + σ.

I and II

Which of the following are true statements about histograms? I. The vertical axis can be either frequencies or relative frequencies. II. They are useful for both small and large data sets. III. One can easily see the shape of the distribution and unusual data values.

I, II, and III

In order to rate TV shows, phone surveys are sometimes used. Such a survey might record several variables, some of which are listed below. Which of these variables are categorical? I. The type of show being watched. II. The number of persons watching the show. III. The gender of persons watching the show. IV. The network on which the show is televised. V. The number of times the show has been watched in the last month.

I, III, and IV

To test the effect of music on productivity, a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is ________________.

a matched pair experiment

A nutritionist wants to study the effect of storage time (6, 12, and 18 months) on the amount of vitamin C present in freeze dried fruit when stored for these lengths of time. Vitamin C is measured in milligrams per 100 milligrams of fruit. Six fruit packs were randomly assigned to each of the three storage times. The treatment, experimental unit, and response are respectively what?

a specific storage time, a fruit pack, amount of vitamin C

A normal probability plot suggests that data is approximately normally distributed when ________________.

a substantial linear pattern is present in the plot

Control groups are used in experiments in order to ________________.

control the effects of outside variables on the outcome

The three principles of experimental design include _____________.

control, randomization, and replication

A personnel director at a large company studied the eating habits of employees by watching the movement of a selected group of employees at lunchtime. The purpose of the study was to determine the proportion of employees who buy lunch in the cafeteria, bring their own lunches, or go out to lunch. If the director includes only employees in one department in her study, she is performing a ______________.

convenience study

The following numbers appear in a table of random digits: 38683 50279 38224 09844 13578 28251 12708 24684 A scientist will be measuring the total amount of leaf litter in a random sample (n = 5) of forest sites selected without replacement from a population of 45 sites. The sites are labeled 01, 02,......45 and she starts at the beginning of the line of random digits and takes consecutive pairs of digits. What is correct about the sample?

her sample is 38, 35, 02, 22, 40

You read in a book about bridge that the probability that each of the four players is dealt exactly one ace is about 0.11. This means that _______________.

in a very large number of bridge deals, the percent of deals on which each player has one ace will be very close to 11%

A researcher for a consumer products company is field testing a new formula for laundry detergent. He has contracted with 60 families, each with two children, who have agreed to test the product. He randomly assigns 30 families to the group that will use the new formula and 30 to the group that will use the company's current detergent formula. The most important reason for this random assignment is that ________________.

randomization is a good way to create two groups of 30 families that are as similar as possible, so that comparisons can be made between the two groups

Lauren is enrolled in a very large college calculus class. On the first exam, the class mean was 75 and the standard deviation was 10. On the second exam, the class mean was 70 and the standard deviation was 15. Lauren scored 85 on both exams. Assuming the scores on each exam were approximately normally distributed, on which exam did Lauren score better relative to the rest of the class?

she scored about equally well on both exams

The National Survey of Adolescent Health interviewed several thousand teens (grades 7 to 12). One question asked was "What do you think are the chances you will be married in the next ten years?" Here is a two-way table of the responses by gender. Female Male Almost no change 119 103 Some chance but probably not 150 171 a 50-50 chance 447 512 A good chance 735 710 Almost certain 1174 756 The percent of females who were almost certain to be married in the next ten years is part of the ______________.

the conditional distribution of opinion among adolescents of a given gender

You want to buy a house in Fort Myers, Florida. Many houses range from $200,000 to $400,000 in price. The few houses on the water, however, have prices up to $15 million. Which of the following statements best describes the distribution of home prices in Fort Myers?

the distribution is most likely skewed to the right, and the mean is greater than the median

The National Survey of Adolescent Health interviewed several thousand teens (grades 7 to 12). One question asked was "What do you think are the chances you will be married in the next ten years?" Here is a two-way table of the responses by gender. Female Male Almost no change 119 103 Some chance but probably not 150 171 a 50-50 chance 447 512 A good chance 735 710 Almost certain 1174 756 The percent of females is part of ________________________.

the marginal distribution of gender

If every observation in a data set is multiplied by 10, the only one of the following that is not multiplied by 10 is ________________.

the mean

A small kiosk at the Atlanta airport carries souvenirs in the price range of $3.99 to $29.99, with a mean price of $14.75. The airport authorities decide to increase the rent charged for a kiosk by 5 percent. To make up for the increased rent, the kiosk owner decides to increase the prices of all item by 50 cents. As a result, which of the following will happen: __________________.

the mean price will increase by 50 cents, but the standard deviation of prices will remain the same

A die is loaded so the number 6 comes up three times as often as any other number. What is the probability of getting a 6 on one toss?

1/2

A fair coin is flipped 5 times. The first four flips lands "heads" up. What is the probability of a "heads" on the next (5th) flip of this coin?

1/2

Scores on the ACT college entrance exam follow a bell-shaped distribution with mean 18 and standard deviation 6. Wayne's standardized score on the ACT was -.07. What was Wayne's actual ACT score?

13.8

The distribution of the heights of students in a large class is roughly Normal. The average height is 68 inches, and approximately 99.7% of the heights are between 62 and 74 inches. Thus, the standard deviation of the height distribution is approximately equal to ______________.

2

In a random sample of spectators who attend either high school football or basketball games but not both, food was purchased in the following amounts. Hot dog Popcorn No Purchase Football 240 80 30 Basketball 50 90 10 What percent of spectators at football games bought popcorn? What percent of hot dog purchasers were at basketball games?

23%; 17%

Select a random integer from -100 to 100. What set of pairs of events are mutually exclusive (disjoint)?

A: the number above 50; B: the number less than 20

George has an average bowling score of 180 and bowls in a league where the average for all bowlers in 150 and the standard deviation is 20. Bill has an average bowling score of 190 and bowls in a league were he average is 160 and the standard deviation is 15. Who ranks higher in his own league, George or Bill?

Bill, because his standardize score is higher than George's

Gina's doctor told her that the standardized score(z-score) for her systolic blood pressure, as compared to the blood pressure of other women her age, is 1.5. What is the best interpretation of this standardized score?

Gina's systolic blood pressure is 1.50 standard deviations above the average systolic blood pressure of women her age.

The National Survey of Adolescent Health interviewed several thousand teens (grades 7 to 12). One question asked was "What do you think are the chances you will be married in the next ten years?" Here is a two-way table of the responses by gender. Female Male Almost no change 119 103 Some chance but probably not 150 171 a 50-50 chance 447 512 A good chance 735 710 Almost certain 1174 756 What percent of females thought that they were almost certain to be married in the next ten years?

about 45%

A personnel director at a large company studied the eating habits of employees by watching the movement of a selected group of employees at lunchtime. The purpose of the study was to determine the proportion of employees who buy lunch in the cafeteria, bring their own lunches, or go out to lunch. The study would best be categorized as ________________.

an observational study

A researcher observes that, on average, the number of divorces in cities with Major League Baseballl teams is larger than in cities without Major League Baseball teams. The most plausible explanation for this observed association is that the _________________.

association is due to the presence of a lurking variable (Major League Baseball teams tend to be in large cities with more people, hence a greater number of divorces)

A maple sugar manufacturer wants to estimate the average trunk diameter of Sugar Maples trees in a large forest. There are too many trees to list them all and take a SRS, so he divides the forest into several hundred 10 meter by 10 meter plots, selects 25 plots at random, and measures the diameter of every Sugar Maple in each one. This is an example of a _____________.

cluster sample

If a distribution is skewed to the right with no outliers, _________________.

mean > median

What is least affected if an extreme high outlier is added to your data?

median

In the northern U.S., schools are sometimes closed during winter due to severe snowstorms. At the end of the school year, schools have to make up the day missed. The following graph shows the frequency distribution of the number of days missed due to snowstorms per year, using data from the past 75 years. What should be used to describe the center of the distribution?

median, because the distribution is skewed and has an outlier

A headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches has disappeared. From this information you conclude ______________.

nothing, because there is no control group for comparison

A researcher reports that the participants in his study lost a mean of 10.4 pounds after two months on his new diet. A friend of yours comments that she tried the diet for two months and lost no weight, so clearly the report was a fraud. What correctly describes the data?

the report gives only the mean. This does not imply that all participants in the study lost 10.4 pounds or even that all lost weight. Your friend's experience does not necessarily contradict the study results

A survey was done in the town of Mechanicsville to estimate the proportion of cars that are red and made by companies based in Japan. A random sample of 25 cars from a student parking lot at Lee-Davis High School was taken. What would not be true of the results of the experiment?

the results will be the same regardless of the time of day that the sample is taken

If 30 is added to every observation in a data set, the only on of the following is not changed is _______________.

the standard deviation

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 some other affiliation. What conclusion seems to be supported by the data?

there is an obvious association between gender and political part registration