A researcher is interested in exploring the relationship between calcium intake and weight loss. Two different groups, each with 25 dieters, are chosen for the study.
Group A is required to follow a specific diet and exercise regimen, and also take a 500-mg supplement of calcium each day.
Group B is required to follow the same diet and exercise regimen, but with no supplemental calcium. After six months on the program, the members of Group A had lost a mean of 12.7 pounds with a standard deviation of 2.2 pounds. The members of Group B had lost a mean of 10.8 pounds with a standard deviation 2.0 pounds during the same time period. Assume that the population variances are not the same.
Create and interpret a 95% confidence interval to estimate the true difference between the mean amounts of weight lost by dieters who supplement with calcium and those who do not.

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Answer:

(0.7044 ; 3.0956)

Step-by-step explanation:

Given:

GROUP A:

n1 = 25

x1 = 12.7

s1 = 2.2

GROUP B :

n2 = 25

x2 = 10.8

s2= 2.0

The obtain the confidence interval assuming unequal population variance :

(x1 - x2) ± tα/2[√(s1²/n1 + s2²/n2)]

The degree of freedom :

df = (s1²/n1 + s2²/n2)² ÷ (s1²/n1)²/n1-1 + (s2²/n2)²/n2-1

The degree of freedom :

(2.2²/25 + 2²/25)² ÷ (2.2²/25)²/24 + (2²/25)²/24

df = 0.12503296 ÷ (0.0015617 + 0.0010666)

df = 47.57 ;

df = 48

Tcritical value ; α = 95% ; df = 48

Tcritical = 2.0106

C.I = (12.7 - 10.8) ± 2.0106[√(2.2²/25 + 2²/25)]

C.I = 1.9 ± (2.0106 * 0.5946427)

C.I = 1.9 ± 1.1955887

C. I = (0.7044 ; 3.0956)