question archive A UCLA researcher claims that the average life span of mice can be extended by as much as 8 months when the calories in their diet are reduced by approximately 40% from the time they are weaned

A UCLA researcher claims that the average life span of mice can be extended by as much as 8 months when the calories in their diet are reduced by approximately 40% from the time they are weaned

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A UCLA researcher claims that the average life span of mice can be extended by as much as 8 months when the calories in their diet are reduced by approximately 40% from the time they are weaned.  The restricted diets are enriched to normal levels by vitamins and proteins. Suppose that a random sample of size 10 mice is fed a normal diet and has an average life span of 32.1 months, with a standard deviation of 3.2 months, while a random sample of 15 mice is fed the restricted diet and has average life span of 37.6 months with a standard deviation of 2.8 months. Test the hypothesis at the 0.05 level of significance, that the average life span of mice on this restricted diet is increased by 8 months against the alternative that the increase is less than 8 months. Assume the distribution of life spans for the regular and restricted diets are approximately normal.      

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Answer:

sample size,n

sample mean,x

standard deviation,s

alpha,a = 0.05

n1= 10 , x1= 32.1 , s1= 3.2000

n2= 15 , x2= 37.6 , s2= 2.8000

H0: u1 = u2

H1: u1 < u2

standard error, SE = sqrt((s1^2/n1)+(s2^2/n2)

SE = 1.24365

test statistic, t = (x1-x2) / SE

t = -4.422

critical value = -t(a,n1+n2-2) = -t(0.05,23)

critical value = -1.714

since t < critical value, hence reject H0

so we conclude that the average life span of mice on this restricted diet is increased by 8 months against the alternative that the increase is less than 8 months