Statistics Question I can't get the correct answer
The time until maturity of a certain variety of tomato plant normally distributed with mean µ and standard deviation σ = 2.4 days. I select a simple random sample of four plants of this variety and measure the time until maturity. The sample yields sample mean = 65. If I wanted the amrgin of error for the 95% confidence interval to be ± 1 day, I should select a simple random sample of what size?