Ch13 Q23. One measure of the exposure of a person to tobacco smoke is the urinary cotinineto creatinine ratio (CCR). (Cotinine is formed in the body by breaking down nicotine.) Scientists measured this ratio in infants om smoking households (Blackburn et a1. 2003). These households were divided into two groups: ones with strict controls to prevent exposure of the infant to smoke (31 babies) and another group with less strict controls (133 babies). The mean (and stande deviation) of the logtransformed CCR was 1.26 (1.58) in the babies from strict households and 2.58 (1.16) from babies om lessstrict households. The distribution of the log-transformed cotinineto-creatinine ratio was approximately normally distributed in both groups. a. Do babies from strict or lessstrict households differ signicantly in their exposure to smoke? Perform an appropriate test. b. On the non-transformed scale, how much higher is the cotinine-tocreatinine ratio in the less strict group, compared to the stricthousehold babies? c. Is this an observational or experimental study? Explain