Question: The following table contains the result obtained by the quality control department of a medium-sized manufacturing concern specializing in the production of a body part widely used in the manufacture of motorcycles.

(a) The production engineer wishes to compare the performance of the four moulds. What would be (i) an appropriate null hypothesis and (ii) an appropriate alternative hypothesis that will enable the production engineer to conduct such a comparison?

(b) Using the data available, is there any reason to believe that the proportion of defective pieces obtained from the different moulds is not the same? Let α=0.05.