Lydia volunteers with an organization that helps older citizens take care of their yards. 75% of the volunteers in the organization are 20-30 years old. Of the remaining portion, 75% are over 30 and 25% are
under 20. If there are 15 people under 20, how many people are in the organization?

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.