1. 1.A neurologist is testing the effect of a drug on response time by injecting 121 rats with a unit dose of the drug, subjecting each to neurological stimulus, and recording its response time. The neurologist knows that the mean response time for rats not injected with the drug is 1.5 seconds. The mean of the 121 injected rats' response time is 1.55 seconds with a sample standard deviation of 0.1 seconds. Do you think that the drug has an effect on raising the response time?

Please describe the relationships and differences between z table and t table.

Please explain in what situation, we have E(XY)=E(X)E(Y), and prove that Var(X+Y-Z)=Var(X)+Var(Y)+Var(Z) under such situation.