Question

In a random sample of 9 residents of the state of New York, the mean waste recycled per person per day was 2.1 pounds with a standard deviation of 0.25 pounds. Determine the 90% confidence interval for the mean waste recycled per person per day for the population of New York. Assume the population is approximately normal.

Step 1 of 2:

Find the critical value that should be used in constructing the confidence interval. Round your answer to three decimal places.

Answer 1

1) df = 9 - 1 = 8

Critical value = t_0.05,8 = 1.860

2) Margin of error = t_0.05,8 * s / sqrt(n) = 1.86 * 0.25 / sqrt(9) = 0.155

Confidence interval = mean + margin of error

                               = (2.1 + 0.155)

                               = (1.945 , 2.255)