First part of AP STATS review

14. In which of the following histograms is the mean less than the median?

*The one that looks like a V*

27. Which of the following distributions has a mean of 60 and standard deviation of 4?

*the hump with 48, 60, 72*

43. If P(A)= .25 and P(B)= .34, what is P (A U B) if A and B are independent?

.505

41. Find the probability of a randomly drawn marble being yellow, given that the marble is small.

0.39

29. A national achievement test is administered annually to 3rd graders. The test has a mean score of 100 and a standard deviation of 15. If Jane's z-score is 1.20, what was her score on the test?

118

8. Why is the IQR considered to be a resistant statistic?

Adding a new extreme observation has little effect on it.

38. Measurements of water quality were taken from a river downstream from an abandoned chemical dumpsite. Concentrations of a certain chemical were obtained from 9 measurements taken at the surface of the water, 9 measurements taken at mid-depth of the water, and 9 measurements taken at the bottom of the water. What type of study was conducted, and what is the response variable of the study?

An observational study was conducted, and the response variable is the concentration of the chemical.

12. Given these parallel boxplots, which of the following is incorrect?

Both sets are skewed to both lower and higher values.

3. What are the categorical variables in your survey?

Everything but average income and family size

13. Which of the following is true about the areas described under the normal curve?

Fewer than one percent of the cases are located three standard deviations above or below the mean.

4. Given that the median is 270 and the interquartile range is 20, which of the following statements is true?

Fifty percent of the data are greater than or equal to 270.

18. Using the regression equation above, correctly interpret the slope.

For every additional streetlight per bloc, the crimes per month decrease by 0.2.

21. A study is conducted relating AP Statistics exam scores to the total number of study hours for the AP Statistics class put in by students during the academic year, and the correlation is found to be .6, which of the following is a true statement?

Higher exam scores tend to be associated with higher numbers of study hours.

46. Which of the following are true? I. Two events are mutually exclusive if they can't both occur at the same time. II. Two events are independent if they have the same probability. III. An event and its complement have probabilities that always add to 1.

I and III only

33. The back-to-back stemplot on the right shows the number of books read in a year by a random sample of college and high school students. Which of the following statements are true? I. One college student read seven books. II. The college median is equal to the high school median. III. The mean is greater than the median in both groups.

I, II, and III

47. Which of the following are true statements? I. The area under a normal curve is always equal to 1, no matter what the mean and standard deviation are. II. The smaller the standard deviation of a normal curve, the higher and narrower the graph. III. Normal curves with different means are centered around different numbers.

I, II, and III

48. A national consumer magazine reported the following correlations. * The correlation between car weight and car reliability is -0.30. * The correlation between car weight and annual maintenance cost is 0.20. Which of the following statements are true?

I, II, and III

11. Which of the following can outliers affect significantly? I. Mean II. Median III. Standard deviation IV. Range V. Interquartile range

I, III, and IV

39. A materials engineer wishes to compare the durability of two different types of paving material. She has 40 different one-mile stretches of interstate highway that she's been authorized to repave for this study. She decides to carry out a matched pairs experiment. Which of the following is the best way for her to carry out the randomization for this study?

Let each of the 40 roadways act as its own pair, dividing each roadway into the first half-mile and the second half-mile. Flip a coin for each of the 40 roadways to decide which half-mile gets which pavement.

34. A bank wishes to survey its customers. The decision is made to randomly pick ten customers who just have checking accounts, ten customers who just have savings accounts, and ten customers who have both checking and savings accounts. This procedure is an example of which type of sampling?

Stratified

49. Staff members of a high school newspaper want to obtain an estimate of the average number of years teachers in the state have been teaching. At an educational conference attended by many teachers in the state, the staff members randomly selected 50 conference attendees and asked the attendees how long they have been teaching. Which of the following describes the sample and the population to which it would be most reasonable for the staff members to generalize the results?

The sample is the 50 conference attendees, and the population is all the conference attendees.

23. Which of the following is a true statement about the correlation coefficient r?

The square of the correlation measures the proportion of the y-variance that is predictable from a knowledge of x.

30. An advantage to using surveys as opposed to experiments is that:

surveys are generally cheaper to conduct

20. To which of the histograms below can the boxplot correspond?

*One with 50-60 being the most and 0-10 being the 2nd most*

40. What's the probability that a randomly selected marble will be blue or white?

0.50

17. Calculate the residual for a block with 10 streetlights and 1 crime a month.

0.6

42. Find the probability of a randomly drawn marble being large, given that the marble is black.

0.65

51. It is estimated that 20 percent of all drivers do not signal when changing lanes. In a random sample of four drivers, what is probability that at least one doesn't signal when changing lanes?

1- (.8)^4

16. You have the following regression equation for the effect of streetlights per block (x), on crimes per month (y): y= 2.4-0.2x How many crimes a month are predicted when there are 7 streetlights on a block?

1.0

7. To the nearest whole number, what percentile is associated with z= -.068?

25th percentile

28. Suppose the scores on an exam have a mean of 75 with a standard deviation of 8. If one student has a test result with a z-score of -1.5, and a second student has a test result with a z-score of 2.0, how many points higher was the second student's result than that of the first?

28

5. In population H, what is the heights, to the nearest tenth of an inch, of the 70th percentile?

67.3 inches

15. A random sample of golf scores gives the following summary statistics: n=20, x= 84.5, Sx= 11.5, minX= 68, Q1= 78, Med= 86, Q3= 91, maxX= 112. What can be said about the number of outliers?

At least 1.

44. An auto analyst is conducting a satisfaction survey, sampling from a list of 10,000 new car buyers. The list includes 2,500 Ford buyers, 2,500 GM buyers, 2,500 Honda buyers, and 2,500 Toyota buyers. The analyst selects a sample of 400 car buyers, by randomly sampling 100 buyers of each brand. Is this an example of a simple random sample?

No, because every possible 400-buyer sample did not have an equal chance of being chosen.

2. You want to know something about your neighbors, so you give them a survey. The survey collects the following data about each family on your block: family size, the kind of pets they have, the grade of the youngest child in the family, the family's average annual income over the last five years, what the dad does for a living, whether the mom works, and their phone number. Each kind of data you collect about a family is a variable. Which of the variables you collect are continuous data?

Only average annual income

32. A company wishes to survey what people think about a new product it plans to market. They decide to randomly sample from their customer database as this includes phone numbers and addresses. This procedure is an example of which type of sampling?

Simple random

10. An airline recorded the number of on-time arrivals for a sample of 100 flights each day. The boxplot below summarizes the records data for one year. Based on the bosplot, which of the following statements must be true?

The difference between the median and the lower quartile for the number of on-time arrivals is less than 2.

1. A scientist recorded the duration of the eruption of the Old Faithful geyser in Yellowstone National Park that occurred during a one-month time period. The histogram below shows the distribution of the duration, in seconds, of the eruptions. Based on the histogram, which of the following is the best description of the distribution?

The distribution displays two clusters with one cluster centered at about 125 seconds and the other centered at about 260 seconds, and has a range of at most 250 seconds.

24. An AP Statistics teacher grades using z-scores. On the second major exam of the marking period, a student receives a grade with a z-score of -1.3. What is the correct interpretation of this grade?

The student scored 1.3 standard deviations lower on the second exam than the class average on the second exam.

36. Which of the following statements is incorrect?

Voluntary response samples often underrepresent people with strong opinions.

35. Two antidepressants are to be compared in the treatment of elderly patients in a nursing home. Each patient has his or her own room, some with spectacular views of the ocean. The experimental design is to create homogeneous blocks with respect to window view. How should randomization be used for a randomized block design?

Within each block, randomly pick half the patients to receive each antidepressant.

37. A critical difference between experiments and observational studies is:

an experiment often suggests a casual relationship, whereas an observational study only suggests an association.

6. In population H, what is the z-score, to the nearest tenth, associated with the heights 65 inches?

z= -0.4