Did I Get This – Hypothesis Testing Overview
Background: Based on the National Center of Health Statistics, the proportion of babies born at low birth weight (below 2,500 grams) in the United States is roughly 0.078, or 7.8% (based on all the births in the United States in the year 2002). A study was done in order to check whether smoking by pregnant women increases the risk of low birth weight. In other words, the researchers wanted to check whether the proportion of babies born at low birth weight among women who smoked during their pregnancy is higher than the proportion in the general population. The researchers followed a sample of 400 women who had smoked during their pregnancy and recorded the birth weight of the newborns. Based on the data, the p-value was found to be 0.016.
The same researchers also wanted to examine whether second-hand smoking (exposure to another person smoking) by pregnant women increases the risk of low birth weight (i.e., the proportion of babies born at a low birth weight among women who were second-hand smokers during their pregnancy is higher than the proportion in the general population). The researchers obtained a sample of 175 pregnant women who were second-hand smokers, followed them during their pregnancies, and found that 10.2% of the newborns had low birth weight. Based on these data, the p-value was found to be 0.119.
This document is linked from Steps in Hypothesis Testing.