The National Survey of Family Growth conducted by the Centers for Disease Control gathers information on family life, marriage and divorce, pregnancy, infertility, use of contraception, and mens and womens health. One of the variables collected on this survey is the age at first marriage. The histogram below shows the distribution of ages at first marriage of 5,534 randomly sampled women between 2006 and 2010. The average age at first marriage among these women is 23.44 with a standard deviation of 4.72. 000 - 800- 600 - 400 200 15 20 25 30 35 40 Age at first marriage a) Assume that the standard deviation of this sample is an accurate estimate of the population sample standard deviation and estimate the average age of US women at first marriage using a 80% confidence interval. Give your answers to two decimal points. 80% confidence interval in years: ( b) Suppose that Canadian women have the same population standard deviation as American women when it comes to age at first marriage. We would like to obtain a 80% confidence interval for the age at first marriage of Canadian women and we would like the margin of error of the interval to be less than one year. How large a random sample do we require? Sample size n =