Statistics
posted by Zodra .
In a study to estimate a population mean, i start with a sample size 10 and calculate the 95% confidence interval. Suppose i am not satisfied with the size of the confidence interval and want to reduce it by half. Give an estimate of sample size that i need.

To reduce the width of a confidence interval in half, you have to multiply the sample size by 4 (in effect quadrupling the sample size).