child health and development studies (chds) has been collecting data about expectant mothers in oakland, ca since 1959. one of the measurements taken by chds is the age of first time expectant mothers. suppose that chds finds the average age for a first time mother is 26 years old. suppose also that, in 2015, a random sample of 50 expectant mothers have mean age of 26.5 years old, with a standard deviation of 1.9 years. at the 5% significance level, we conduct a one-sided t-test to see if the mean age in 2015 is significantly greater than 26 years old. statistical software tells us that the p-value = 0.034.