The analysis has been restricted to this particular group in order to avoid dealing with the risks associated with plural births, parity, prior birth history, marital status, and race. The variables available from birth certificates that might be useful in examining this cohort of births are age, education, smoking, and prenatal care. It must be kept in mind that other variables that are unavailable for our analysis of data from birth certificates might also have a bearing on birth weight outcomes. We will examine the risk of smoking cigarettes on low birth weight deliveries. In this analysis, the outcome, birth weight, is identified as either less than 2,500 grams or 2,500 grams or more.
Smoking is categorized as either smoker or non-smoker.
However, it has marginal utility in explaining the nature of the disease or condition and usually cannot be used to suggest causation. X 2 statistic. Using data from the 2x2 table of smoking risk, we can insert the appropriate numbers according to the above formula to then calculate the Chi-square. The probability that the difference in birth weight outcomes between smokers and non-smokers is due to chance is less than 1 in 1,000. Bounds Age 15 or less 1.09 0.17 0.96 to 1.