A random sample of 30 students spent an average amount of $40.00 on a date, with a standard deviation of $5.00. The standard error of the sample mean is 0.913. Calculate an approximate 95% confidence interval for the average amount spent by all students on a date.
A) (40.00, 90.00)
B) (79.10, 80.90)
C) (78.20, 81.80)
D) None of the above

Question

Quizplus · Accepted Answer

The standard error of the mean is calculated as the standard deviation divided by the square root of the sample size. In this case, the standard error of the mean is $5.00 / sqrt(30) = 0.913.The 95% confidence interval is calculated as the sample mean plus or minus 1.96 times the standard error of the mean. In this case, the 95% confidence interval is $40.00 +/- 1.96 * 0.913 = (78.20, 81.80).

A Random Sample of 30 Students Spent an Average Amount