1. A study investigated the impact of smoking on a person’s ability to become pregnant. Of 135 female smokers in the stu

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1. A study investigated the impact of smoking on a person’s
ability to become pregnant. Of 135 female smokers in the study, 38
became pregnant in the first cycle after going off birth
control.
(a) What is the explanatory variable in this study? What is the
responding variable? What might be a potential confounding
variable?
(b) Describe the shape, center and standard error of a sampling
distribution based on this sample.
(c) Find and interpret a 95% confidence interval for the
proportion of females smokers who become pregnant in the first
cycle after going off birth control.
(d) Does the data provide evidence that the proportion of female
smokers who become pregnant in the first cycle after going off
birth control is less than 50%? Show all details of the relevant
test and make a conclusion in context.
(e) What sample size would we need to use if we want a margin of
error within ±2% and a confidence interval of 99%?