Previous research has shown that the mean number of ballpoint pens Americans use per year is 4.3 with a standard deviation of 1.17. You believe that amount is too high since computers are used so...

Previous research has shown that the mean number of ballpoint pens Americans use per year is 4.3 with a standard deviation of 1.17. You believe that amount is too high since computers are used so often this day and age. You randomly select 20 people and find the average to be 3.8 ballpoint pens per year. Assuming normality, is there evidence to show that the mean has decreased? What is the test statistic for this hypothesis test?