Stastic Exam Sheet

Example Sheet 3

1. What Z-value is associated with a 95% confidence interval?

A. 1.28

B. 1.65

C. 1.96

D. 2.58

C

2. Which of the following is NOT a property of the t distribution?

A. It is symmetric.

B. Its exact shape (i.e., spread) is characterized by the degrees of freedom.

C. As the sample size grows, it gradually approaches the normal distribution.

D. All of the above are properties of the t distribution.

D

3. A 95% confidence interval for the mean can be interpreted to mean which of the following?

A. If all possible samples are taken and confidence intervals calculated, 95% of those intervals would include the true population mean somewhere in their interval.

B. You can be 95% confident that you have selected a sample whose interval includes the population mean.

C. Both answers #1 and #2 are correct.

D. Neither answer #1 nor #2 is correct.

C

4. Two random samples have sizes of n=49 and n=36 respectively. Which of the following is true for a 95% confidence interval?

A. The sample of n=36 has a greater degree of confidence.

B. The sample of n=49 has a greater degree of confidence.

C. The confidence interval for the sample of n=49 is narrower.

D. The confidence interval for the sample of n=49 is wider.

A and C

5. The Z value selected for constructing a given confidence interval is also called what?

A. The Z value is also called the critical value.

B. The Z value is also called the student value.

C. The Z value is also called the confidence value.

D. The Z value is often called the error value.

A

6. A sample of 50 students was taken from the local university. These students spent an average of $170 on books this

semester, with a standard deviation of $25.50. Which