Twelve dieters lost an average of 5.2 pounds in 6 weeks when given a special die

Question

Twelve dieters lost an average of 5.2 pounds in 6 weeks when given a special diet plus 28) a "fat-blocking" herbal formula. A control group of twelve other dieters were given the same diet, but without the herbal formula, and lost an average of 4.5 pounds during the same time. The standard deviation of the "fat-blocker" sample was 2.8 and the standard deviation of the control group was 2.5. Find the 95% confidence interval for the differences of the means. A) -0.4 < 1 - 2 < 1.8 B) -1.7 < 1 - 2 < 3.1 C) -1.2 < 1 - 2 < 2.6 D) -1.8 < 1 - 2 < 0.4

Explanation / Answer

df=(12-1)+(12-1)=22

95% confidence interval

==>t=(look from the t table at 22 & 95%)

difference in means=5.2-4.5=0.7

so confidence interval is (0.7-t*sqrt[ (s12/n1) + (s22/n2) ] , 0.7+t*sqrt[ (s12/n1) + (s22/n2) ])

Substitute the values in the equation.

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