refer to the indicated data set in Appendix B and use the Wilcoxon rank-sum test. IQ and Lead Exposure ?Data Set 5 in Appendix B lists full IQ scores for a random sample of subjects with medium lead levels in their blood and another random sample of subjects with high lead levels in their blood. Use a 0.05 significance level to test the claim that subjects with medium lead levels have full IQ scores with a higher median than the median full IQ score for subjects with high lead levels. Does lead level appear to affect full IQ scores?

Solution 9BSC Step 1 : Given, In the above example the data consists of the IQ scores for a random sample of subjects with medium lead levels in their blood and another random sample of subjects with high lead levels in their blood , so the observations from the same population. Hence first requirement of the Wilcoxon Rank-Sum test satisfied. Each samples contains 12 values, it satisfies the second condition that the each sample should have the same median. Therefore, both the requirements of the Wilcoxon Sum-Rank test satisfies. Hypothesis : H 0 The median of full IQ scores for a random sample of subjects with medium levels is equal to the median of full IQ scores for a random sample of subjects with high levels H 1 The median of full IQ scores for a random sample of subjects with medium levels is not equal to the median of full IQ scores for a random sample of subjects with high levels. Step 2 : We have 24 observations from Flight 19 and 21. Based on the values we give ranks, if it is least value then rank will be 1 and next to the value will be 2 and so on. If there is a tie then mean of the values is the rank, Ranks for sample 1 are 2, 16, 12, 8, 24, 21, 15, 20, 1, 23, 6.5, 10 The sum of the ranks for sample 1 = 158.5