A statistics professor has 115 students in a statistics class and would like to estimate the number of hours each student studied for the last exam. A random sample of 24 students was found to study an average of 6.8 hours with a standard deviation of 2.2 hours. The 90% confidence interval to estimate the average number of hours studying for the exam is ________.
A)(5.79, 7.81)
B)(5.86, 8.74)
C)(6.69, 6.91)
D)(6.11, 7.49)

Question

Quizplus · Accepted Answer

The 90% confidence interval is calculated using the formula: mean ± (t-value * (standard deviation/√n)). With a sample size of 24, the t-value for 90% confidence is approximately 1.711. Plugging in the values: 6.8 ± (1.711 * (2.2/√24)) gives the interval (6.11, 7.49).

A Statistics Professor Has 115 Students in a Statistics Class