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Tue 31 Jul, 2012 02:20 pm
On the basis of the results obtained from a random sample of 100 men from a particular district, the 95% confidence interval for the men height of the men in the district is found to be (177.22 cm, 179.18 cm).
a) Find the value of the mean of the sample (x) and the sample standard deviation (s).
b) Calculate the 90% confidence interval for the mean height.
c) Calculate the 95% confidence interval for the variance of the height.
@shezie,
a) The mean is in the middle of the confidence interval for a normally distributed population.
b) The z score for the 95% confidence interval is 1.96 so take the upper limit minus the mean from part a and divide by 1.96 to get the standard deviation. The z score for 90% confidence interval is 1.645, so multiply the standard deviation by 1.645, then add and substract from the mean to get the new interval.
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