Please explain

Working Backwards from the Condence Interval to Find the Sample Size If researchers desire a specic margin of error, then they can use the error bound formula to calculate the required sample size. Suppose a population parameter is known to have a standard deviation of 2. If the researchers want to be 95% condent that the sample mean is within 0.1 of the true population mean, what sample size should be used? (Round to the nearest whole number.) \"=