The dataset birthweight.wf1contains 3000 observations of live births in Pennsylv

Question

The dataset birthweight.wf1contains 3000 observations of live births in Pennsylvania (the file birthweight.pdf provides variable definitions). The variable birthweight is infant weight (in grams). The dummy variable smoker is equal to 1 for mothers who smoked during pregnancy and zero for those who did not. NPREVIST the number of pre-natal visits received during pregnancy. 1. What is the average birthweight for all 3000 infants? (hint: just run LS birthweight C). 3. Run the model LS birthweight c smoker NPREVIST (show output) d. What is the new 95% confidence interval for the coefficient on smoker? e. What does the changing value for the coefficient on smoker lead you to conclude about the model with only smoker as a right hand side variable? EViews File Command LS birthweight c smoker Proc Quick Options Add-ins V Hel E Equation: UNTITLED Workfile: BIRTHWEIGHT (1)-Untitled View Proc Object Print Name Freeze Estimate Forecast Stats Resids Coeficient Confidence Intervals Sample: 1 3000 Included observations: 3000 View Proc Obj Range: 1 Sample: 1 3000 Date:09/27/18 Time: 01:32 age alcohol birthweight 90% CI 95% CI 99% C1 Variable Coefficient Low High Low High High drinks educ nprevist resid smoker 3432.060 3412.528 3451.592 3408.784 3455.336 3401.463 3462.657 -253.2284 -297.5733 208 8834-306.0736 200.3831 -322.6950 -183.7617 SMOKER tripre1 tripre2 tripre3 unmarried Path clusers lao yangidocuments DB none WF- birthweight (1)

Explanation / Answer

1. For this part, see the last screenshot from bottom in the question.

a. The estimated regression equation is -
Birthweight = 3382.934
In this regression equation, there is only a constant term and no variable. Hence, the average birthweight will be 3382.934.

3. The output is shown in the second screenshot in the question. The estimated regression equation:

BIRTHWEIGHT = 3050.527 -218.83*SMOKER + 34*NPREVISIT

d. The 95% confidence interval is given by the below formula -

estimate of SMOKER's coefficient +/- Std Error*1.96
Or, -218.83 +/-1.96*26.49
Or, -218.83 +/- 51.92

The 95% confidence interval = (-218.83 - 51.92,-218.83 + 51.92)
= (-270.75,-166.91)

e. It tells us that pre-natal visits also positively affect the birth weight. The absolute coefficient of SMOKER decreased after including NPREVIST. It could be possible that pre-natal visits provide information to pregnant women to improve their and baby's healthcare.

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