A pacemaker manufacturer is considering using a new electrode, which must adhere to a silicon substrate for many years. The company performs an experiment using a sample of 25 volunteers to test the hypothesis that the mean adherence time is 20 years against the alternative that it is less than 20 years at a significance level of a -0.05. Assume the population distribution for adherence time is approximately normal. The average adherence time for the pacemakers in the 25 volunteers is found to be 18.8 years with a standard deviation of 3 years i. Is the null hypothesis rejected? ii. The company would like to decrease the probability of making a type I error without increasing the sample size (which would require waiting another 20 years to get the results!). Should the critical value be increased or decreased? Briefly explain how this can be done Find the 90% confidence interval for the population variance,
