Question

(CO 4) In a sample of 15 stuffed animals, you find that they weigh an average of 8.56 ounces with a standard deviation of 0.09 ounces. Find the 92% confidence interval.

Answer 1

92% Confidence Interval = [8.515, 8.605]

Explanation:

The number of samples given is 15,this less than 30, hence, we use the t score confidence Interval

= Mean ± t score × Standard deviation/√n

Mean = 8.56 ounces

Standard deviation = 0.09 ounces

n = 15

We find the degrees of freedom = n - 1

= 15 - 1 = 14

Using the T score table

T score for 92% confidence interval with degrees of freedom 14

= 1.8875

Hence:

Confidence Interval =

= 8.56 ± 1.8875 × 0.09/√15

= 8.56 ± 0.0454010035

Confidence Interval

8.56 - 0.0454010035

= 8.5145989965

≈ 8.515

8.56 + 0.0454010035

= 8.6054010035

≈ 8.605

92% Confidence Interval = [8.515, 8.605]