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Table 1 Precision estimates for effect sizes given varied assumptions about control-arm prevalence and between-community variation

From: A community mobilisation intervention to prevent violence against women and reduce HIV/AIDS risk in Kampala, Uganda (the SASA! Study): study protocol for a cluster randomised controlled trial

Outcome

Estimated final sample size per site (with 4 intervention and 4 control sites in total)

Estimated prevalence of outcome measure

Effect estimate

Estimate of precision of percentage risk difference (95% CI)*

  

Control arm (%)

Intervention arm (%)

Risk difference (%)

k = 0.1

k = 0.2

k = 0.3

k = 0.4

Past year experience of physical IPV (women partnered in past year)

75 (based on 100 respondents per site, 80% having partner in past year and 5% non-response to violence questions)

30.0

22.5

7.5

−2.4, 17.4a

−5.2, 20.2 a

−8.8, 23.8 a

−12.9, 27.9 a

  

30.0

15.0

15.0

5.8, 24.2

3.4, 26.6

0.2, 29.8

−3.4, 33.4 a

  

20.0

15.0

5.0

−3.2, 13.2 a

−4.7, 14.7 a

−6.9, 16. 9 a

−9.4, 19.4 a

  

20.0

10.0

10.0

2.4, 17.6

1.1, 18.9

−0.8, 20.8 a

−3.0, 23.0 a

Past year experience of sexual IPV (women partnered in past year)

75 (based on 100 respondents per site, 80% having partner in past year and 5% non-response to violence questions)

15.0

11.0

4.0

−3.1, 11.1 a

−4.1, 12.1 a

−5.6, 13.6 a

−7.3, 15.3 a

  

15.0

7.5

7.5

0.9, 14.1

0.0, 15.0

−1.3, 16.3 a

−2.8, 17.8 a

  

10.0

7.5

2.5

−3.4, 8.4 a

−3.9, 8.9 a

−4.8, 9.8 a

−5.8, 10.8 a

  

10.0

5.0

5.0

−0.4, 10.4 a

−0.9, 10.9 a

−1.7, 11.7 a

−2.6, 12.6 a

Concurrent sexual partners (among non-polygamous men partnered in the past year)

75 (based on 100 respondents per site, 80% having partner in past year and 5% non-response to sexual behaviour questions)

50.0

37.5

12.5

0.0, 25.0

−5.7, 30.7 a

−12.5, 37.5 a

−19.7, 44.7 a

  

50.0

25.0

25.0

13.4, 36.6

8.4, 41.6

2.4, 47.6

−3.9, 53.9 a

  

40.0

30.0

10.0

−1.3, 21.3 a

−5.5, 25.5 a

−10.7, 30.7 a

−16.3, 36.3 a

  

40.0

20.0

20.0

9.5, 30.5

5.9, 34.1

1.3, 38.7

−3.7, 43.7 a

  1. *Based on calculations provided by Hayes and Bennet (1999) [58].
  2. aNo statistically significant difference between intervention and control groups.
  3. IPV, intimate partner violence.