Answers to Chapter 5

Test Yourself

Return to Ch 5 Test Yourself

Question #1:

None of the interactions are significant, therefore they shouldn't be included in the equation.

Regression Table:

Question: Does Drinking water source have an impact on weight/age z score controlling for SES (roof) and education?
Dependent Variable: WAZ
Independent Variable

Model Number: coefficient (t,p)

1

2

3

4

5

6

7

8

9

10

11

12

13

14
Dummy Good Drinking water

0.314 (2.252, 0.025)

-

0.258 (1.794, 0.073)

-0.310 (-0.682, 0.495)

0.244 (1.687, 0.092)

-0.279 (-0.611, 0.541)

-

0.178 (1.219, 0.223)

-

0.163 (1.115, 0.265)

0.194 (1.346, 0.179)

0.233 (0.855, 0.393)

0.273 (1.936, 0.053)

0.03848 (0.200, 0.842)
Dummy Med. Drinking water

0.005133 (0.049, 0.961)

-

-0.04294 (-0.395, 0.693)

-0.03389 (-0.312, 0.755)

0.162 (0.615, 0.539)

0.128 (0.486, 0.627)

-

-0.0852 (-0.777, 0.438)

-

-0.0864 (-0.788, 0.431)

-0.0716 (-0.661, 0.509)

0.112 (0.689, 0.491)

-0.00994 (-0.094, 0.925)

-0.0414 (-0.317, 0.751)
Toilet Access

-

0.242 (2.117, 0.035)

0.224 (1.876, 0.061)

0.181 (1.472, 0.141)

0.278 (2.058, 0.040)

0.228 (1.613, 0.107)

-

0.08540 (0.663, 0.507)

-

0.06814 (0.526, 0.599)

-

-

-

-
Interaction (dgooddrwat *toilet)

-

-

-

0.627 (1.318, 0.188)

-

0.581 (1.207, 0.228)

-

-

-

-

-

-

-

-
Interaction (dmeddrwat *toilet)

-

-

-

-

-0.245 (-0.855, 0.393)

-0.195 (-0.674, 0.501)

-

-

-

-

-

-

-

-
Roof

-

-

-

-

-

-

0.359 (3.786, 0.000)

0.304 (2.801, 0.005)

-

0.283 (2.572, 0.010)

0.323 (3.231, 0.001)

0.448 (3.312, 0.001)

-

-
Interaction (dgooddrwat * roof)

-

-

-

-

-

-

-

-

-

-

-

-0.111 (-0.344, 0.731)

-

-
Interaction (dmeddrwat * roof)

-

-

-

-

-

-

-

-

-

-

-

-0.331 (-1.516, 0.130)

-

-
Educational Attainment

-

-

-

-

-

-

-

-

0.267 (2.733, 0.006)

0.122 (1.180, 0.238)

-

-

0.195 (1.940, 0.053)

0.07095 (0.489, 0.625)
Interaction (dgooddrwat * edu)

-

-

-

-

-

-

-

-

-

-

-

-

-

0.509 (1.787, 0.074)
Interaction (dmeddrwat * edu)

-

-

-

-

-

-

-

-

-

-

-

-

-

0.109 (0.488, 0.626)
N

775

803

773

773

773

773

802

770

806

770

772

772

775

775
Adjusted R2

0.005

0.004

0.008

0.009

0.007

0.008

0.016

0.016

0.008

0.017

0.017

0.017

0.008

0.01

 

Question #2:
Regression Table

Question: Does delivery location have an affect on weight/age z score controlling for SES and education?
Dependent Variable: WAZ
Independent Variable

Model Number: coefficient (t,p)

1

2

3

4

5

6
Delivery Location

0.438 (4.529, 0.000)

0.414 (4.203, 0.00)

0.372 (3.747, 0.000)

0.351 (3.464, 0.001)

-

-
Toilet Access

-

0.148 (1.284, 0.199)

0.005182 (0.041, 0.967)

-0.009443 (-0.074, 0.941)

-

-
Roof

-

-

0.288 (2.708, 0.007)

0.269 (2.501, 0.013)

0.359 (3.786, 0.000)

-
Educational Attainment

-

-

-

0.115 (1.116, 0.265)

-

0.267 (2.733,0.006)
N

798

798

798

798

801

805
Adjusted R2

0.024

0.025

0.032

0.033

0.018

0.009

 

From this summary table it is clear that delivery location is significantly associated with waz and remains significant after controlling for sanitation, SES and educational attainment. As the delivery location coefficient changes little between models, there is no confounding between the other independent variables and delivery location. However, if you look at toilet access in models one and two, the coefficient changes by a large degree, indicating confounding, but note that it is  insignificant in each model.