A researcher has computed confidence limits for the population mean for a sample of n = 128 with M = 20 and s x = 5.66, finding P{19.02≤μ≤20.98}=0.95. If the researcher wants to reduce the confidence...

A researcher has computed confidence limits for the population mean for a sample of n = 128 with M = 20 and s_x
= 5.66, finding P{19.02≤μ≤20.98}=0.95.

If the researcher wants to reduce the confidence interval by half, other things being equal, the researcher should try a random sample of size: