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Table 3 Regression model predicting variability in response rates in placebo groups of clinical trials; n = 153 studies/comparisons; formal and diagnostic variables (ICD coding)

From: The therapeutic effect of clinical trials: understanding placebo response rates in clinical trials – A secondary analysis

 

Beta

t (DFs = 142)

p-value

Constant

 

2.07

0.04

Duration in months

0.31

6.17

<0.000001

Multicenter trial

0.13

3.04

0.003

Quality Index

0.18

3.44

0.0008

Neoplasms (C)

-0.21

-5.48

<0.000001

Organical psychological disorders (F0)

-0.12

-3.24

0.001

Disorders due to substance abuse (F1)

-0.14

-2.97

0.003

Nervous diseases (G)

-0.10

-2.55

0.01

Prevention trial

0.44

7.94

<0.000001

Quality rating: Additional treatment described?

-0.21

-4.34

0.00003

Quality rating: Dropouts described?

-0.16

-3.33

0.001