Question

30 35 23 22 28 39 21 Population 2 45 49 15 34 20 49 36 Use this data to find the 90% confidence interval for the true difference between the population means. Assume that both populations are normally distributed. Step 3 of 4 : Calculate the margin of error to be used in constructing the confidence interval. Round your answer to six decimal places.

Answer 1

(−14.850850 ; 0.565135)

Explanation:

Confidence interval :

Xd ± Tcritical * Sd/√n

Population 1 :30 35 23 22 28 39 21

Population 2 : 45 49 15 34 20 49 36

d = -15,-14,8,-12,8,-10,-15

The mean of d, Xd = Σx / n = - 7.14285714

The standard deviation of the difference, Sd = 10.4948967 (using calculator)

Sample size, n = 7

Tcritical at 90%, df = 7 - 1 = 6

Tcritical = 1.943176

Confidence interval :

- 7.14285714 ± 1.943176 * 10.4948967/√7

Confidence interval :

- 7.14285714 ± 7.7079925

(−14.850850 ; 0.565135)