The standard deviation of a sample is estimated to be 80 and the standard error has been calculated to be 5. What size of sample will the researcher need to ensure a 90% confidence interval (Z=1.64)?
A) 256
B) 420
C) 688
D) 1640

Question

Quizplus · Accepted Answer

The sample size (n) can be calculated using the formula for the standard error of the mean: Standard Error = Standard Deviation / sqrt(n). Rearranging this formula to solve for n gives n = (Standard Deviation / Standard Error)^2. Substituting the given values (Standard Deviation = 80, Standard Error = 5) gives n = (80 / 5)^2 = 16^2 = 256.

The Standard Deviation of a Sample Is Estimated to Be