I was given this word problem:
The weekly earnings of students in one age group are normally distributed with a standard deviation of 88 dollars.
A researcher wishes to estimate the mean weekly earnings of students in this age group.
Find the sample size needed to assure with 98 percent confidence that the sample mean will not differ from the population mean by more than 2 dollars.
A. 239 B. 120 C. 26 D. 10511 E. 4504
Should I use invNorm or invT for this problem?
For invNorm (.01), I got -2.33.
For invT (.01, 87), I got -2.37.
Also, I have no idea on how to plug "more than 2 dollars" into the confidence interval.