AP Stat - Review

Here is the dot plot of voter turnout (as a percentage of voting-age population) for the 50 states—plus the District of Columbia—in a recent presidential election. Which of the following best describes this distribution?

• The distribution of voter turnout is skewed slightly left, centered at about 62%, with a range of 24%.
• The distribution of voter turnout is roughly symmetric, centered at about 60%, with a range of 30%.
• The distribution of voter turnout is skewed slightly right, centered at about 62%, with a range of 24%.
• The distribution of voter turnout is bimodal, centered at about 60%, with a range of 30%.

Independently selected groups of middle-school children were given a poem to memorize. After a certain period of time, they were asked to recall as much of the poem as they could. A back-to-back stem plot of the distribution of the number of words that each group of children could correctly remember is displayed above. Which of the following statements about these data is true?

• There are more students in Group 1 than in Group 2.
• The third quartile of the Group 1 distribution is larger than the maximum value of the Group 2 distribution (that is, 25% of the Group 1 values are larger than any Group 2 value).
• The median of the Group 2 distribution is smaller than the first quartile of the Group 1 distribution (that is, 50% of the Group 2 values are smaller than at least 75% of Group 1 values).
• The mean number of words remembered for Group 1 is smaller than the mean number of words remember for Group 2.

The side-by-side boxplots show the distribution of test scores in Ms. Williams’s two sections of calculus. Based on these boxplots, which one of the following statements must be true?

• The lowest score in A period was close to the 15th percentile of the C period class.
• The mean score for students in C period was higher than the mean score for students in A period.
• More people scored between 72 and 90 in C period than scored between 72 and 81 in A period.
• The standard deviation of scores in A period is smaller than the standard deviation of scores in C period.

Joe Mama wants to do an observational study comparing height and weight. He also does a study comparing weight and calories consumed daily. He concludes that the more calories you consume, the more you weigh. And people who weigh more are generally taller. Therefore, if you eat more, you will get taller. Why is this incorrect?

• Causation from one observational study cannot be extrapolated and applied to another

• Correlation does not indicate causation

• He is ignoring the lurking variable of age

• He did not have a control group

Frannie and Fiona collect data comparing students' GPA and how many hours per week they spend doing extracurricular activities. This is best described as a(n)

• observational study

• matched pairs design

• experiment

• survey

The mean temperature in Glens Falls for the month of February is 23 degrees with a standard deviation of 4.2 degrees.  What is the z-score for a temperature of 17 degrees?  

• 1 
• 1.43
• -1.43
• 11.5

If I tell you that you scored at the 55th percentile on your last exam, you would know:

• 55% of the class scored as good or worse than I did.

• I earned a 55% on the exam.

• I failed the exam.

• 45% of the class scored worse than I did.

Every possible group of units of the required size has the same chance of being the selected sample as any other sample of the same size.

• Simple Random 
• Thoughtful
• Typical
• Proportional

This sample is selected by dividing the population into subgroups and then taking a fixed number of units from each group using the simple random sample.

• stratified
• cluster
• judgment
• experimental

In a certain school, students can choose whether to eat in the school’s cafeteria. A reporter working for the school’s newspaper polled students on their reactions to changes in the menu at the cafeteria. For each student leaving the cafeteria in one 20-minute time period, the reporter used a die to determine whether to stop the student and ask how he or she felt about the new menu. In the reporter’s article it was stated that a random sample of the students showed that 23% of the school’s student population was happy with the new menu. Which of the following statements is true?

• Because each student leaving the cafeteria was randomly selected and could choose to answer or not, this is a random sample of the student population, and the 23% is an accurate measurement of the school population’s view of the new menu.

• Because students self-selected whether to eat in the cafeteria, the sampling method might be biased and the sample might not be representative of all students in the school.

• The survey would have been more effective if the reporter had collected the data in one 10-minute time period rather than in one 20-minute time period.

• The survey would have been more effective if students who cared about the food could have called the reporter to tell how they felt about the new menu, so that only students with opinions on the subject would have been surveyed.

• Because no treatment was imposed on the students eating in the cafeteria, one cannot make any conclusions about the new menu.