- A study is conducted to estimate the mean completion time of a task to within 1 minute 36 seconds of the population mean. Suppose completion time is normally distributed with a standard deviation of 7 minutes 6 seconds. What minimum sample size is required at the 86.9% confidence level? You must use a critical 2 value rounded to two (2) decimal places. Do not round other intermediate results. Report final answer as an integer. Minimum sample size required = C] Question Help: El Video Check