Question

Given two dependent random samples with the following results: Population 1 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 1 of 4: Find the point estimate for the population mean of the paired differences. Let x1 be the value from Population 1 and x2 be the value from Population 2 and use the formula d=x2−x1 to calculate the paired differences. Round your answer to one decimal place.

Answer 1

(-14.8504 ; 0.5644)

Explanation:

Given the data:

Population 1 : 30 35 23 22 28 39 21

Population 2: 45 49 15 34 20 49 36

The difference, d = population 1 - population 2

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

The confidence interval, C. I ;

C.I = dbar ± tα/2 * Sd/√n

n = 7

dbar = Σd/ n = - 7.143

Sd = standard deviation of d = 10.495 (using calculator)

tα/2 ; df = 7 - 1 = 6

t(0.10/2,6) = 1.943

Hence,

C.I = - 7.143 ± 1.943 * (10.495/√7)

C.I = - 7.143 ± 7.7074

(-14.8504 ; 0.5644)