Suppose that a researcher is planning a new study on hemoglo

Suppose that a researcher is planning a new study on hemoglobin levels amongst women under 25 years old. Previous research suggest that the standard deviation of hemoglobin is 0.7 g/dl. In the new study the research wants to have the standard error for the sample mean to be no more than 0.05 g/dl. Find the required sample size for the new study.

Solution

std error = std dev / sqrt(n)

=> n = (std dev / std error)^2 = (0.7 / 0.05)^2 = 196