Question

In a random sample of 12 12 residents of the state of Montana, the mean waste recycled per person per day was 2.2 pounds with a standard deviation of 0.84 pounds. Determine the 90% confidence interval for the mean waste recycled per person per day for the population of Montana. 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

Step 1)

df = n - 1= 12 -1 = 11

t critical value at 0.10 significance level with 11 df = 1.796

Step 2)

90% confidence interval for is

- t * S / sqrt(n) < < + t * S / sqrt(n)

2.2 - 1.796 * 0.84 / sqrt(12) < < 2.2 + 1.796 * 0.84 / sqrt(12)

1.7645 < < 2.6355

90% CI is ( 1.7645 , 2.6355)