Question

A sample of 10 students record their scores on the final exam for their statistics class. The mean of the sample is 81 with sample standard deviation 7 points. Analysis of the 10 sample values indicated that the population is approximately normal. We wish to find the 95% confidence interval for the population mean test scores.

1. What is the confidence level, c?
2. Which of the following is correct?
   1. To find the confidence interval, a z-critical value should be used because the population standard deviation is known.
   2. To find the confidence interval, a t-critical value should be used because the population standard deviation is known.
   3. To find the confidence interval, a z-critical value should be used because the population standard deviation is not known.
   4. To find the confidence interval, a t-critical value should be used because the population standard deviation is not known.
3. What are the degrees of freedom?
4. Find t_c (to three decimal places).
5. Find the error, E, of the confidence interval (round your answer to 3 decimal places).
6. Which of the following gives the 95% confidence interval for the population test score?
   1. (85, 86.007)
   2. (80, 90)
   3. (75.993, 86.007)
   4. (75.993, 85)
   5. (74.745, 87.334)
   6. (73.485, 87.341)

Answer 1