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Table 4 Frequency of risk of bias judgements in each bias domain across included outcomes

From: The effect of changing the built environment on physical activity: a quantitative review of the risk of bias in natural experiments

Risk of bias judgement

Pre-intervention

At-intervention

Post-intervention

Overall bias

Bias due to confounding

Bias in selection of participants into the study

Bias in measurement of interventions

Bias due to departures from intended interventions

Bias due to missing data

Bias in measurement of outcomes

Bias in selection of the reported result

Low

-

-

6

8

8

1

-

-

Moderate

-

7

4

3

4

-

-

-

Serious

14

7

5

4

2

11

15

3

Critical

1

1

-

-

-

3

-

12

No information

-

-

-

-

1

-

-

-