A manufacturing company wishes to estimate the number of items that its workforce can produce on average each hour now that they have a new machine. The factory examined the records for a random sample of 8 hours over the past month. The hourly production rates for these 8 hours were:
142 175 162 158 190 154 160 185
a) Calculate by hand and interpret the 99 percent confidence interval for the average number of items produced per hour.
b) What assumption did you make in order to answer part (a)?