Elementary Statistics Written Homework
No software output is required for this assignment.
1. 6.58 Multiple-choice questions on Advanced Placement exams have five options: A, B, C, D, and E. A random sample of the correct choice on 400 multiple-choice questions on a variety of AP exams shows that B was the most common correct choice, with 90 of the 400 questions having B as the answer. Does this provide evidence that B is more likely than 20% to be the correct choice?
a. State the hypotheses and calculate the sample statistic.
Ho: All choices are equally probable.
Ha: B is more likely to be the correct choice.
b. Are conditions met for using a Normal distribution for this test? Explain.
c. Calculate the standard error and z-test statistic, assuming a Normal distribution is appropriate.
d. Find the p-value and draw a Normal curve with appropriate shaded region. You may give either a precise p-value from software or bounds on the p-value from Table A.
p-value: 0.106
e. State the conclusion of the test in context, using nontechnical language.
f. Find a 95% confidence interval for the proportion of questions on all AP exams having B as the correct choice using the normal distribution and the formula for standard error. Show your calculations.