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Table 4 Principal strata for both compliance and pregnancy as IOs

From: Intermediate outcomes in randomized clinical trials: an introduction

 

Treatment assigned

 

Sample space of final outcome: preeclampsia

 

Control

Treatment

  

Principal strata

Treatment

Pregnant (0 = placebo; 1 = calcium)

Treament received (0 = no; 1 = yes)

Pregnant (0 = no; 1 = yes)

Labels

Assigned to control

Assigned treatment

Proportion in the stratum

(Average treatment assigned ) Effect

1

0

0

0

0

Never-takers never pregnant

*

*

p1

*

2

0

0

0

1

Never-takers pregnant under treatment

*

(no, yes)

p2

*

3

0

0

1

0

Compliers never-pregnant

*

*

p3

*

4

0

1

0

0

Never-takers pregnant under control

(no, yes)

*

p4

*

5

1

0

0

0

Defiers never-pregnant

*

*

0

*

6

0

0

1

1

Compliers pregnant under treatment

*

(no, yes)

p6

*

7

0

1

0

1

Never-takers always-pregnant

(no, yes)

(no, yes)

p7

0

8

1

0

0

1

Defiers pregnant under treatment

*

(no, yes)

0

*

9

0

1

1

0

Compliers pregnant under control

(no, yes)

*

p9

*

10

1

0

1

0

Always-takers never-pregnant

*

*

p10

*

11

1

1

0

0

Defiers pregnant under control

(no, yes)

*

0

*

12

0

1

1

1

Compliers always-pregnant

(no, yes)

(no, yes)

p12

Ï„12

13

1

0

1

1

Always-takers pregnant under treatment

*

(no, yes)

p13

*

14

1

1

0

1

Defiers always-pregnant

(no, yes)

(no, yes)

0

Ï„14

15

1

1

1

0

Always-takers pregnant under control

(no, yes)

*

p15

*

16

1

1

1

1

Always-takers always-pregnant

(no, yes)

(no, yes)

p16

0

  1. *Final outcome or effect not defined; **it is possible in theory to have always-takers, because women can take calcium supplementation out of the trial intervention.