A researcher wants to test whether there is a difference in the average number of hours high schoolers and college students spend on their phones. They have samples of 40 high schoolers and 40 college students and an approximate number of hours the students spend on their phones every day. What test should the researcher use?

According to a study conducted in 2015, 18% of shoppers said that they prefer to buy generic instead of name-brand products. suppose that in a recent sample of 1500 shoppers, 315 stated that they prefer to buy generic instead of name-brand products. at a 5% significance level, can you conclude that the proportion of all shoppers who currently prefer to buy generic instead of name-brand products is higher than .18? use both the p-value and the critical-value approaches.