A head librarian supervises a number of libraries in a largecounty. He wants to know if full-time library workers and part-timelibrary workers re-shelve books at the same rate. So, he checks therecords of 45 full-time library workers and finds that theyre-shelve an average of 166 books per hour with a standarddeviation of 9.3 books per hour. The records of 45 part-timelibrary show that they re-shelve an average of 159 books per hourwith a standard deviation of 12.2 books per hour.
Using a level of significance of α=.01, is there enough evidenceto indicate a difference in the mean number of books re-shelved byfull-time workers compared to part-time workers?
please be detailed in telling how to locate the z= 1.645 and z=-1.645
