In: Statistics and Probability
777
We selected a random sample of n = 50 male adults. The sample men produced an average of x = 542 grams of fat per day with a standard deviation of s = 13.6 grams of fat per day. Based on this sample, construct a 95% confidence interval for the mean daily production of fat for the men.
Then find 99% CI and compare to the 95% CI.
Given :
Since population standard deviation is unknown ( not given ) , we need to use t-interval.
The formula is ,
First we need to find the 95% confidence interval ,
So c = 0.95
Degrees of freedom = n - 1 = 50 - 1 = 49
Using excel function ,
Now plug the values in the formula ,
Therefore the 95% confidence interval for the mean daily production of fat for the men is ( 538.1341 , 545.8659 )
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Now we need to find the 99% confidence interval ,
c = 0.99
df = 49
Usinge excel function ,
Now plug the values in the formula ,
Therefore the 99% confidence interval for the mean daily production of fat for the men is ( 536.8455 , 547.1545 )
The 99% confidence interval for the mean daily production of fat for the men is wider than the 95% confidence interval for the mean daily production of fat for the men .