Smoking during pregnancy is a known cause of reduced infant birth weight and other issues that can affect the delivery and mortality. Despite this strong evidence, women who smoke find it difficult to quit even when they are pregnant. Suppose a study is done measuring the birth weight of babies of mothers who smoked during pregnancy and those who did not smoke. The birth weight data in pounds are:
Smokers: 3.1, 4.2, 4.5, 5.0, 6.4, 4.7, 6.0
Nonsmokers: 5.5, 6.5, 7.1, 8.0, 6.8, 7.5, 6.2
a. State the hypotheses for conducting a one-sided (right tailed) Wilcoxon test.
b. Find the ranks for the two groups and their mean ranks.
c. Software reports a small-sample one-sided P-value of 0.022. Interpret.