Question: Suppose a newspaper surveys 250 adults about their cell phone carrier. The percentages listed are 30%, 30%, 10%, 20%, and 5%. Does this table describe a relative frequency distribution? Why or why not?

Answer Options: A. No. The sum of the relative frequencies is 95%, not 100%. B. No. The percents must be written as decimals in a relative frequency distribution. C. No. Frequencies should be stated instead of percents. D. Yes. Categories are given, along with their corresponding percents.

Answer: A. No. The sum of the relative frequencies is 95%, not 100%. 2

Question: A stem-and-leaf plot of daily high temperatures is right-skewed. Which measures of center and spread are most appropriate?

Answer Options: A. Median and interquartile range B. Mean and interquartile range C. Mean and standard deviation D. Median and standard deviation

Answer: A. Median and interquartile range 3

Question: A boxplot has no visible line inside the box to indicate the median. Why?

Answer Options: A. The median value is equal to either the first or third quartile. B. The median could not be computed for this data. C. The median value is equal to the third quartile. D. The median value is equal to the first quartile.

Answer: A. The median value is equal to either the first or third quartile. 4

Question: A frequency distribution has frequencies 1, 1, 7, 13, 6, 2, 1. Do the data appear to have a distribution that is approximately normal?

Answer Options: A. No, it is approximately uniform. B. Yes, it is approximately normal. C. No, it is completely erratic. D. No, it is not at all symmetric.

Answer: B. Yes, it is approximately normal. 5

Question: Why might it be inappropriate to use a designed experiment to assess the effects of taking prenatal vitamins on newborn health?

Answer Options: A. A designed experiment would suffer more than an observational study from confounding and lurking variables. B. A designed experiment would not allow the researcher to claim causation, only association. C. Since there is a perceived benefit to taking prenatal vitamins, there would be ethical issues in intentionally denying them to some pregnant women. D. A designed experiment would be retrospective and require women to remember whether they took prenatal vitamins.

Answer: C. Since there is a perceived benefit to taking prenatal vitamins, there would be ethical issues in intentionally denying them to some pregnant women. 6

Question: Why do Realtors report median existing-home prices instead of the mean?

Answer Options: A. Home prices are probably skewed left, so low-priced homes would pull down the mean. B. Home prices probably have a symmetric distribution. C. Home prices are probably skewed right, so extremely high-priced homes would pull up the mean and make the typical home appear more expensive. D. Home prices are discrete data, so the median must always be used.

Answer: C. Home prices are probably skewed to the right and not symmetric. The mean would be influenced by extremely high-priced homes and could make the typical home price appear higher than it is. 7

Question: A research center called 1047 adults after their telephone numbers were randomly generated by a computer. Which type of sampling was used?

Answer Options: A. Systematic sampling B. Random sampling C. Stratified sampling D. Convenience sampling E. Cluster sampling

Answer: B. Random sampling 8

Question: Twelve nutritionists are each paid $100,000 to try a celebrity diet on clients and report the results. What is wrong with this study?

Answer Options: A. The results have statistical significance but not practical significance. B. The sample of nutritionists is self-selected. C. The sample of clients is self-selected. D. The nutritionists have a special interest in obtaining results favorable to their backers.

Answer: D. The nutritionists have a special interest in obtaining results that are favorable to their backers. 9

Question: What is the trend in the number of indoor movie theaters, and how does it compare with drive-in theaters?

Answer Options: A. There is an upward then downward trend, unlike drive-ins, which only have a downward trend. B. There is an upward trend, unlike drive-in movie theaters, which have a downward trend. C. There is a downward trend, similar to drive-in theaters.

Answer: B. There appears to be an upward trend, unlike drive-in movie theaters, which have a downward trend. 10

Question: Based on the sampling distribution of sample variances, is the sample variance an unbiased estimator of the population variance?

Answer Options: A. The sample variance targets the population variance. As such, the sample variance is an unbiased estimator. B. The sample variance targets the population variance. As such, it is biased. C. The sample variance does not target the population variance. As such, it is unbiased. D. The sample variance does not target the population variance. As such, it is biased.

Answer: A. The sample variance targets the population variance. As such, the sample variance is an unbiased estimator of the population variance. 11

Question: Golden retriever weights are normally distributed. Samples have size n=15. Is it correct to conclude that the sample means cannot be normally distributed because the sample size is too small?

Answer Options: A. Yes the sample size must be over 30. B. No as long as more than 30 samples are collected. C. No because the samples are randomly collected. D. No the original population is normally distributed, so sample means are normally distributed for any sample size.

Answer: D. No; the original population is normally distributed, so the sample means will be normally distributed for any sample size. 12

Question: Why can the normal distribution be used for the distribution of sample mean female pulse rates when the sample size is only 4?

Answer Options: A. Since the mean pulse rate exceeds 30. B. Since the distribution is of sample means. C. Since the original population has a normal distribution, the distribution of sample means is normal for any sample size. D. Since the distribution is of individuals.

Answer: C. Since the original population has a normal distribution, the distribution of sample means is a normal distribution for any sample size. 13