AP STATISTICS REVIEW

EXPERIMENTAL DESIGN

100

Which of the following is most important in minimizing the placebo effect? A) Replication and randomization B) Replication and blinding C) Randomization and blinding D) Randomization and a control E) Blinding and a control

What is E? Use of a control group and blinding as to which subjects are in the control group are the best tools to minimize the possibility of confounding due to the placebo effect. Replication and randomization are important marks of good experimental design, but they do not impact the placebo effect as does the use of a control and blinding.

200

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? A) Cluster B) Convenience C) Simple random D) Stratified E) Systematic

What is D? In stratified sampling the population is divided into homogeneous groups called strata, and random samples of persons from all strata are chosen. In this example, the bank stratified by type of account holding into three strata.

300

Advantage(s) to using surveys as opposed to experiments is (are) that I. Surveys are generally cheaper to conduct II. It is generally easier to conclude cause and effect from surveys. III. Surveys are generally not subject to bias. A)I only B)II only C)III only D)I and II E)II and III

What is A? Surveys are generally cheaper and quicker to conduct than experiments; however surveys are subject to bias, and it is very difficult to conclude cause and effect from surveys.

400

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? A) Cluster B) Convenience C) Simple Random D) Stratified E) Systematic

What is B? Convenience samples are based on choosing individuals who are easy to reach.

500

Sampling error occurs A) When interviewers make mistakes resulting in bias. B) When interviewers use judgement instead of random choice in picking the sample. C) When samples are too small. D) Because a sample statistic is used to estimate a population parameter. E) In all of the above cases.

What is D? Different samples give different sample statistics, all of which are estimates for the same population parameter, and so error, called sampling error, is naturally present.

PROBABILITY

100

Suppose 80% of jurors come to a just decision. In a jury of six people, what is the probability more than half come to a just decision? A) .09888 B) .34464 C) .8 D) .90112 E) .98304

What is D? 1 - P(3 or fewer) = 1-binomcdf(6,.8,3)

200

53% of adults say they have trouble sleeping. If a doctor contacts an SRS of 85 adults, what is the probability that over 55% will say they have trouble sleeping? A) .3109 B) .3558 C) .3640 D) .4000 E) .6442

What is B? np=85(.53)=45 >10 and nq=85(.47)=40 > 10. The sampling distribution is approximately normal with mean .53 and standard dev. .0541 normalcdf(.55, 1, .53, .0541) = .3558

300

If P(A)=.25 and P(B) = .34, what is P(A or B) if A and B are independent? A) .085 B) .505 C) .590 D) .675 E) There is insufficient information to answer this question.

What is B? P(A or B) = .25 + .34 - (.25)(.34) = .505

400

An inspection procedure at amanufacturing plant involves picking three items at random ant then accepting the whole lot if at least two of the three items are in perfect condition. If in reality 84 percent of the whole lot are perfect, what is the probability that the whole lot will be accepted? A) .560 B) .593 C) .667 D) .706 E) .931

What is E? (.84)(.84)(.84)+3(.84)(.84)(.16) = .931

500

There are five outcomes to an experiment and a student calculates the respective probabilities of the outcomes to be .34, .50, .42, 0, and -.26. The proper conclusion is that A) The sum of the individual probabilities is 1. B) One of the outcomes will never occur. C) One of the outcomes will occur 50% of the time. D) All of the above are true. E) The student made an error.

What is E? Probabilities are never less than 0.

INFERENCE

100

In general, how does doubling the sample size change the confidence interval size? A) Doubles the interval size B) Halves the interval size C) Multiplies the interval size by 1.414 D) Divides the interval size by 1.414 E) This question cannot be answered without knowing the sample size.

What is D? Increasing the sample size by a multiple of d divides the interval estimate by the square root of d.

200

What is the probability of a Type II error when a hypothesis test is being conducted at the 5% significance level? A) .05 B) .10 C) .90 D) .95 E) There is insufficient information to answer this question.

What is E? There is a different probability of Type II error for each possible correct value of the population parameter.

300

A guidance counselor wishes to determine the mean number of changes in academic major by college students to within + or - 0.1 at a 90 percent confidence level. What sample size should be chosen if it is known that the standard deviation is 0.45? A) 8 B) 54 C) 55 D) 78 E) 110

What is C? 0.1 = 1.645(0.45) / (sqroot n) n= 55

400

A confidence interval estimate is determined from the summer earnings of SRS of n students. All other things being equal, which of the following will result in a larger margin of error? I. A greater confidence level II. A larger sample standardard deviation III. A larger sample size A) I and II B) I and III C) II and III D) I, II, and III E) None of the above gives the complete set of true responses.

What is A? The margin of error varies directly with the critical z-value and directly with the standard deviation of the sample, but inversely with the square root of the sample size.

500

A college recruiter is interested in comparing the SAT math and verbal scores of applicants to the college. An SRS of 40 applicants is chosen, and the math and verbal scores are noted. Which of the following is a proper test? A) Test of difference in two population means. B) Test of difference in two population proportions. C) One sample test on differences of paired data. D) Chi-square goodness-of-fit test. E) Chi-square test for homogeneity.

What is C?

AP STAT LANGUAGE

100

Explain what 95% confidence means.

What is in several random samples, 95% of the confidence intwervals produced will contain the true parameter for the population.

200

Explain what the p-value means.

What is the probability of obtaining the sample result if the null hypothesis is true.

300

Explain what the r-squared tells you.

What is the percent of the variation in the y that is accounted for by the linear regression model on x.

400

The interpretation of the standard deviation of a statistic.

What measures the typical distance of the values in a distribution from the mean?

500

Interpretation of the slope of a LSRL.

What is, as the explanatory variable increases by 1 unit, the response variable will increase by b.