QUESTION 19 A firm aims to have 95% confidence in estimating the proportion of office workers who respond to an email in less than an hour to within ± 0.05. A survey has never been undertaken before, so no past data is available. The firm believes that if the proportion is 0.5, then this will result in the largest variability in the sample proportion. Based on this, determine the sample size needed using the approximate value of z = 2 for the 95% confidence interval. Justify the choice of 0.5 for the proportion.