An industrial designer wants to determine the average amount of time it takes an adult to assemble an “easy to assemble” toy. a sample of 16 times yielded an average time of 19.9 minutes, with a sample standard deviation of 6 minutes. assuming normality of assembly times, provide a 90% confidence interval for the mean assembly time.

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.