Question

A high school teacher at a small private school assigns trigonometry practice problems to be worked via the net. Students must use a password to access the problems and the time of log in and log off are automatically recorded for the teacher. At the end of the week, the teacher examines the amount of time each student spent working the assigned problems. The data is provided below in minutes.

49 48 43 39 34 33 28 27 25 25 22 22 22 20 15

The value of t is?

Construct a 99% confidence interval on the true average time the student spent working the assigned problems.

Answer 1

= (49 + 48 + 43 + 39 + 34 + 33 + 28 + 27 + 25 + 25 + 22 + 22 + 22 + 20 + 15)/15 = 30.13

S = sqrt(((49 - 30.13)^2 + (48 - 30.13)^2 + (43 - 30.13)^2 + (39 -30.13)^2 + (34 - 30.13)^2 + (33 - 30.13)^2 + (28 - 30.13)^2 + (27 - 30.13)^2 + (25 - 30.13)^2 + (25 - 30.13)^2 + (22 - 30.13)^2 + (22 - 30.13)^2 + (22 - 30.13)^2 + (20 - 30.13)^2 + (15 - 30.13)^2)/14) = 10.4872

At 99% confidence interval the critical value is t^* = 2.977

The 99% confidence interval for population mean is

+/- t^* * s/

= 30.13 +/- 2.977 * 10.4872/

= 30.13 +/- 8.061

= 22.069, 38.191