You measure 22 backpacks' weights, and find they have a mean weight of 39 ounces. Assume the population standard deviation is 14.8 ounces.

Question

Based on this, construct a 90% confidence interval for the true population mean backpack weight.

Give your answers as decimals, to two places

Answer 1

Confidence interval = mean +/- z-critical * standard deviation/square root(sample size)

Here the mean is 39, the standard deviation is 14.8, the sample size is 22.

for a 90% confidence interval, the z critical value is the z-score corresponding to a 0.95 probability = 1.645.

39 +/- 1.645 * 14.8/sqrt(22) = 39 +/- 5.19 = 33.81,44.19