To Compute the Necessary Sample Size for an Interval Estimate

Multiple Choice

To compute the necessary sample size for an interval estimate of a population mean, all of the following procedures are recommended when σ is unknown except​

A) ​use the estimated σ from a previous study.
B) ​use the sample standard deviation from a preliminary sample.
C) ​use judgment or a best guess.
D) use .5 as an estimate.