Exercise 8:    Interaction tests

·         This exercise will use demo2 project. If you have not started demo2 project, click here to follow exercise 1: start the new project demo2

·         This exercise will use new variables. Click here to follow through Exercise 2:  Create new variables, code and label variables, if you have not done so.

Objectives:

·         Create interaction tests table 1

·         Create interaction tests table 2

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Objective 1: To create following table:

Interactions test 1

 

-

No

Yes

Total

P(interaction)

SBP

Crude

0.5 (-0.3, 1.3) 0.233

-0.5 (-1.7, 0.6) 0.368

0.2 (-0.5, 0.8) 0.651

0.155

Adjusted

1.0 (0.2, 1.7) 0.011

0.4 (-0.6, 1.5) 0.409

0.8 (0.2, 1.4) 0.011

0.430

DBP

Crude

0.3 (-0.1, 0.7) 0.137

-0.4 (-1.0, 0.2) 0.172

0.1 (-0.3, 0.4) 0.671

0.049

Adjusted

0.4 (0.0, 0.8) 0.032

-0.1 (-0.7, 0.5) 0.771

0.3 (-0.1, 0.6) 0.114

0.140

 

ß(95%CI) p-value or OR/RR(95%CI) p-value

Outcome: SBP and DBP , Risk factor: Body mass inex

Crude: none adjusted

Adjusted: adjust for AGE, SEX, Education, Occupation and Alcohol consumption

Interaction p-value were from log likelihood ratio test comparing two nested models

 

Follow following steps to create the above table:

·         Click “Advanced analysis” -> “Interactions test”

·         Drag and drop variable SBP and DBP to “Select outcome variables (Y)”

·         Drag and drop BMI to “Select risk factors(X)”

·         Drag and drop AGE, SEX, EDUC, OCCU and ALH to “Model 2 (Adjusted)”.

·         Drag and drop SMK to “Select effect modifier (categorical)”

·         Set rows sorted by “Y: Outcomes” then “M: Models” and then “X: Exposures”

 

  

 

·         Click “View Table” button, wait for a few seconds, you will get the above table

 

Done!

Objective 2: To create following table:

Interactions test 2

 

SNP marker I

Cigarette smoking

N

Mean ± SD

beta

95% CI

P value

P(interaction)

SBP

AA

No

297

126.3 ± 2

0.0

0.288

AA

Yes

183

129.5 ± 2

-6.4

-10.9, -2.0

0.004

AB

No

156

132.1 ± 2

6.5

2.8, 10.2

0.001

AB

Yes

101

137.6 ± 2

4.9

-0.1, 9.9

0.055

BB

No

15

137.7 ± 1

11.6

1.6, 21.5

0.023

BB

Yes

23

140.3 ± 2

7.5

-1.2, 16.3

0.092

DBP

AA

No

297

68.5 ± 1

0.0

0.257

AA

Yes

183

69.2 ± 1

-1.4

-3.9, 1.0

0.248

AB

No

156

69.4 ± 1

1.1

-0.9, 3.2

0.278

AB

Yes

101

72.1 ± 1

2.4

-0.3, 5.2

0.083

BB

No

15

70.8 ±

2.0

-3.5, 7.5

0.472

BB

Yes

23

72.0 ± 1

2.4

-2.4, 7.3

0.322

 

Outcome: SBP and DBP

Risk factor: SNP marker I

Adjust for: AGE, Body mass inex, SEX, Education, Occupation and Alcohol consumption

Interaction P value were from log likelihood ratio test comparing 2 nested models

Follow following steps to create the above table:

·         Click “Advanced analysis” -> “Interactions test”

·         Drag and drop variable SBP and DBP to “Select outcome variables (Y)”

·         Drag and drop SNP1 to “Select risk factors(X)”

·         Drag and drop AGE, BMI, SEX, EDUC, OCCU and ALH to “Model 1”.

·         Drag and drop SMK to “Select effect modifier (categorical)”

·         Set rows sorted by “Y: Outcomes” then “X: Exposures”.

             

·         Click “View Table” button, wait for a few seconds, you will get the above table

 

Done!