The data file ncbirth.sav is a sample of birth records taken by the North Carolina State Center for Health and Environmental Statistics. The data set represents a sample of 1450 births taken within the state of North Carolina. Of particular interest will be incidents of Low Infant Birth Weight. Low birth weight has been associated with weaker development of many characteristics such as intelligence, coordination, strength, etc. Low birth weight is commonly defined as less than 2500 grams (approximately 88.18 ounces).

The variables examined are:

Answer the following questions. Answers to questions need to be properly labeled. Use SPSS output to support your answers wherever it is needed. SPSS outputs have to be also properly labeled and referenced in your answers, summaries or conclusions.  Be aware of data value "98" in the variables cigs and drinks. Find a reasonable way (or form) to include them in the analysis unless the variable is not considered in the analysis.

1. Dichotomize the totounc variable using 88.18 ounces as the cutoff and save it as btotounc which will have value 1 if underweight and have value 0 if over 88.18 ouonces. Create an indicator variable for smoking status, name it bsmoke. This variable will have a value 1 for indicating the mother smoked and 0 indicating the mother did not smoke.  Create an indicator variable from drinks, name it bdrankal.  This variable will have a value 1 for indicating the mother drank and 0 indicating the mother did not drink. Create an indicator variable, bmothed, for whether a mother completed high school or not (0 if mothed £ 12, 1 if mothed > 12).
• Perform a logistic regression for predicting btotounc using bsmoke, bdrankal, bmothed, mothage, and gest as predictor variables. Identify the significant factors of giving birth to low birth weight child. Include the SPSS output to explain your findings.
• What was the odds ratio of having low birth weight child for smoking mothers versus non-smoking mothers? What was the odds ratio of having low birth weight child for mothers who drank alcohol versus non-drinker? What was the odds ratio of having low birth weight child for mothers who had less than 12 years of education versus those who had more years of education? Interpret these odds ratios?
2. The odds ratio for studying a risk factor can be calculated from a simple 2 by 2 contingency table and can also be estimated from a logistic regression model as in problem 3. Is there any difference between these two odds ratios? If yes, explain the difference and the advantages and/or disadvantages for each method.
3. What are the limitations of the analysis above?