Can you use a spreadsheet for the calculations using the proper formulas?

Question 12

The director of admissions at the University of Maryland, University College is concerned about the high cost of textbooks for the students each semester. A sample of 25 students enrolled in the university indicates that x(bar) = $315.40 and s = $43.20.

Using a significance level of .1, what are the boundaries of the confidence interval for the population mean?

Question 12 options:

- 282.871 - 338.475

- None of the answers match my calculation.

- 297.485 - 327.820

- 300.618 - 330.182

- 302.438 - 326.184

Question 13

Does the confidence interval in Question 12 reject mean $300?

Question 13 options:

- Yes, because 300 is below the lower limit of the confidence interval.

- No, because 300 is below the lower limit of the confidence interval

- No, because 300 is in the confidence interval

- Yes, because 300 is in the confidence interval

Question 14

The director of admissions at the University of Maryland, University College, is concerned about the high cost of textbooks for the students each semester. A sample of 25 students enrolled in the university indicates that x(bar) = $315.40 and s = $75. (Note the sample standard deviation is different from the first part).

At the 0.05 level of significance, does the new confidence interval reject the mean $300?

Question 14 options:

- Yes, because 300 is in the confidence interval

- No, because 300 is in the confidence interval

- No, because 300 is below the lower limit of the confidence interval

- Yes, because 300 is below the lower limit of the confidence interval

Question 15

Explain the difference between questions 12 and 14. In questions we are asked whether or not there is evidence against a population mean of $300.

In Question 12: x(bar) = $315.40; s = $43.2; n = 25

In Question 14: x(bar) = $315.40; s = $75.0; n = 25

Question 15 options:

- The smaller standard error indicated the sample may have had some outliers and increases the width of the confidence interval.

- The larger standard deviation in Question 14 reflects greater spread in the sample data indicating that the sample may have had some outliers, increasing the width of the confidence interval.

- The smaller mean adds uncertainty in the sample. The sample may have had some outliers.

- The larger mean adds uncertainty in the sample. The sample may have had some outliers.