Construct a confidence interval at a 98% confidence level.

Question

In a survey, 20 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $47 and standard deviation of $6.

Answer 1

CI = mean +/- t-critical * SD/sqrt(sample size)

t-critical is t-score for 19 degrees of freedom and alpha/2 = 0.01