Question: A researcher is interested in studying people’s mean age in a certain region. If the population standard deviation is known to be 8 years and 1.5 year of error margin is allowed, find the minimum simple size the researcher needs to use, knowing that he is going to conduct his study using 95% confidence level.   Edit

Answer: Here margin of error E = 1.5, population std. deviation σ =8 and confidence interval is 95% hence Zα/2 = 1.96. So the sample size n = (Zα/2 * σ / E )^2 = (1.96 * 8 / 1.5)^2 = 109.27 ~ 110 (Ans.)   Edit