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# Sheet1 headcirc,length,gestage,birthwt,momage,toxemia 27,41,29,1360,37,0 29,40,31,1490,34,0 30,38,33,1490,32,0 28,38,31,1180,37,0 29,38,30,1200,29,1

Use the dataset low_birth_weight_infants.dta.
a. (1.5) Do a linear regression to model birth weight as the dependent variable and gestational age as the independent variable:
The equation is: _____________________
The coefficient of determination is: ______________________
The p-value for the slope is: ___________________

b. (2.5) Add length as another independent variable to the above regression model.
The equation is: _____________________
The coefficient of determination is: ______________________
The p-value for the gestage coefficient is: ___________________
The p-value for the length coefficient is: ___________________
Do you think the model improves by adding length as an independent variable (yes/no) _____? Explain.

c. (2) Compute a 95% confidence interval for the true mean of birth weight with a gestational age of 31 weeks and a length of 40 cm. Round off to whole numbers.
d. (2) Create an interaction term by multiplying gestational age and length. Add the interaction term to the model that already includes gestage and length. Fill in the table (left column without interaction, right column with interaction term).
Independent variables
gestage, length gestage, length, gestlength
p-value, gestage coefficient
Std error, gestage coefficient
p-value, length coefficient
Std error, length coefficient
Coefficient of determination
e. (1) What principle accounts for the changes in p-value and standard error?
f. (1) Since the coefficient of determination rose slightly, would you include the interaction term in the model? Why or why not?

Sheet1 Page 1 headcirc,length,gestage,birthwt,momage,toxemia 27,41,29,1360,37,0 29,40,31,1490,34,0 30,38,33,1490,32,0 28,38,31,1180,37,0 29,38,30,1200,29,1 23,32,25,680,19,0 22,33,27,620,20,1 26,38,29,1060,25,0 27,30,28,1320,27,0 25,34,29,830,32,1 23,32,26,880,26,0 26,39,30,1130,29,0 27,38,29,1140,24,0 27,39,29,1350,26,0 26,37,29,950,25,0 27,39,29,1220,25,0 26,38,29,980,28,0 29,42,33,1480,30,0 28,39,33,1250,31,1 27,38,29,1250,37,0 25,36,28,920,31,0 25,38,30,1020,21,0 24,34,27,750,21,0 31,42,33,1480,30,0 28,37,32,1140,23,0 23,32,28,670,33,1 26,36,29,1150,18,0 25,34,28,1030,20,0 23,33,29,560,29,0 28,37,30,1260,26,0 35,36,31,900,23,0 24,31,30,620,33,0 33,39,31,1440,26,0 28,39,29,1350,38,0 26,37,27,1170,23,0 26,36,27,1170,23,0 26,37,27,1170,26,0 28,40,32,1420,27,0 29,43,31,1475,27,0 28,37,28,1200,19,0 27,36,30,970,30,1 27,38,29,1190,27,0 28,39,28,1350,31,0 28,41,31,1460,29,0 22,32,27,570,23,1 22,32,25,620,35,0 28,40,30,1200,27,0 24,32,28,660,35,0 28,40,28,1280,28,0 23,33,25,830,21,0 22,31,23,680,26,0 23,32,27,640,21,0 28,39,28,1440,29,0 25,38,27,1150,32,0 27,35,27,850,32,0 24,29,26,760,24,0 23,20,25,620,19,0 21,32,23,660,41,0 25,35,26,985,33,0 22,33,24,690,17,0 27,38,29,1200,26,1 28,40,29,1370,20,0 26,35,27,1170,25,0 28,38,30,1200,30,0 27,39,30,1100,32,0 31,43,32,1480,33,0 30,38,33,1350,34,1 26,38,27,1160,23,0 27,38,31,1330,30,0 24,36,26,960,22,0 25,39,27,1080,35,0 25,36,27,1000,26,0 29,41,35,1490,34,1 25,35,28,880,18,1 29,41,30,1370,23,0 31,40,31,1325,18,1 29,39,30,1400,20,0 26,37,27,1240,29,0 23,31,25,660,18,0 23,34,25,780,25,0 25,37,26,950,14,0 25,36,29,850,39,0 28,40,29,1200,32,0 30,42,34,1440,35,1 26,38,30,1100,23,1 26,38,29,1250,18,0 29,42,33,1420,28,1 28,38,30,1400,19,0 27,36,29,1420,36,0 24,34,24,900,29,0 29,38,33,1160,33,1 23,34,25,820,39,0 28,41,32,1410,29,1 27,39,31,1300,33,1 26,38,31,1110,30,0 26,37,31,820,30,1 27,40,29,1150,28,0 28,35,32,880,35,1 28,41,33,1320,36,1 26,38,28,1080,36,0

Great question... View the full answer

1)
S
UMMARYOUTPUT
Regression S
tatistics
Multiple R
RS
quare
quare
S
tandard Error
Observations 0.660
0.436
0.430
203.884
100 ANOVA
Regression
Residual
Total df
1
98
99 SS
3143019.07...

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