One of a treatment (a nutritionally enriched environment) or a control (no nutritional enrichment) are randomly selected to be applied to each of a number of otherwise similar seeds. After a fixed time, the resulting seedling plants are dried and then weighed. Armed with the results of this study, which tool would you use to evaluate the claim that 25% of the treatment plants will have a weight greater than 5 grams?

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.