Question

7. (4 marks) In 2017 at a mechanic's shop 35% of customers needed wheel or brake re- pairs, 40% needed engine repairs, 10% needed bodywork repairs, 10% needed electrical repairs, and 5% needed interior repairs. The mechanic wants to know if those proportions are still accurate in 2020. He randomly selects 90 repairs performed so far in 2020 and finds the following data. Type of repair Wheel/Brake Engine Bodywork Electical Interior Count 44 7 11 2 26 Have the proportions of repairs changed from the 2017 values? Test using a = 0.05. 8. (4 marks) A seafood restaurant often receives complaints from it's patrons that the lobster is too small. The menu lists the weight of a lobster as 462g. The next time the restaurant receives a batch of 60 lobsters it weighs them and finds the average is 451g with a standard deviation of 33g. Do you think the restaurant sells lobsters that are smaller than advertised? Perform a hypothesis test at a = 0.01.

Answer 1

7)

op (DP-ep) Yep el 26 35690 31.5 0.9603 100 44 1. 7778 7 you go 36 100 10 90 100 9 156901100)- 4.5 १ 0.4444 = 2 alol 0.4444 1.3889, 90 5.0158 - Ho: The proportions of repairst not changed from 247 values HI: The proportions of repairs changed from 2017 values - Test statistie: gpV+ 3 (602-epy go: 15.0158 stat ) df: KY5-1= 4 let us be a-0.05 (from * -table) Xcxp = 9.4877 s sence , Star < 9.4877, we fail to gefect Ho cant condude that the proportions of repairs changed from the 2017 values. we