11. (1 + 1+ 1 + 1 = 4 marks) A manufacturer of automatic washers provides particular model in one of three colors - white, black, and grey. It was noted that of 1000 washers sold 320 were black. Do the sample data provide sufficient sample evidence to conclude that the proportion of the customers who prefer black washers is different from 1/3? Test the appropriate hypothesis using critical value approach. Use level of significance a = 0.05. a. State null and research hypotheses: H : H, : b. Find the observed value of test statistic. Keep 2 digits after decimal point in the expression for observed value of test statistics. The observed value of test statistic is Zobs. c. State the rejection region. The rejection region is d. Insert the word sufficient or insufficient into the following statement. There is sample evidence that the proportion of the customers who prefer black washers is different from 1/3