Table 4 Design based strategies

Drummond et al., 2008 [34]

General questions vs topic related questions first

1.17

0.96, 1.43

Survey delivery mode

Intervention

Hocking et al., 2006 [35]

Postal survey vs telephone interview

2.66

2.02, 3.52

Shosteck and Fairweather, 1979 [36]

Postal survey vs telephone interview

1.03

0.68, 1.55

Seguin et al., 2004 [37]

Postal survey vs email survey

2.00

1.67, 2.38

Pooled

1.82

1.19, 2.78

Scott et al. 2011 [24]

Online survey vs mixed mode

0.73

0.51, 1.04

Online survey vs sequential mixed mode

0.65

0.44, 0.97

Online survey vs Simultenous mixed mode

0.83

0.55, 1.26

Advance contact

Drummond et al., 2008 [34]

Letter pre-contact letter vs no pre-contact

1.10

0.91, 1.35

Pirotta et al., 1999 [38]

Postcard pre-contact vs no pre-contact

1.30

0.98, 1.72

Pooled

1.16

0.99, 1.37

Gattellari et al., 2012 [13]

Mail pre-contact vs fax pre-contact

1.11

0.87, 1.43

McLaren and Shelley, 2000 [30]

Telephone pre-contact vs postcard pre-contact

1.01

0.73, 1.40

Gupta et al., 1997 [39]

Medical researcher pre-contact vs non-medical researcher

1.33

0.87, 2.05

Ward et al., 1998 [33]

GP phonecall pre-contact vs other interventions

1.39

1.02, 1.88

Pen pre-contact vs other interventions

0.97

0.73, 1.30

Letter pre-contact vs other interventions

0.95

0.71, 1.26

Research assistant phonecall pre-contact vs other interventions

0.86

0.68, 1.09

Reminders

Bonevski et al., 2011 [40]

Telephone reminder vs none

1.21

0.68, 2.15

Tracking

Akl et al., 2011[41]

Tracking of reponses for follow up vs No tracking

0.85

0.59, 1.23

Personalisation and GP group endorsed letters

Bonevski et al., 2011[40]

Sponsorship letter vs standard letter 1^st mailout

1.38

0.86, 2.22

Gattellari et al., 2012 [13]

Coloured seal with text vs coloured seal without text

1.08

0.84, 1.38

Maheux et al., 1989[42]

Handwritten ‘thank you’ postscript with 1st reminder vs no postscript

1.45

0.92, 2.30

Maheux et al., 1989[42]

Personalised mail out package vs Non-personalised mail out package with 2^nd reminder

1.73

1.04, 2.87

Timing of mailing

Akl et al., 2011[41]

Friday vs onday mailing

1.86

1.28, 2.69

Olivarius and Andreasen, 1995 [43]

Saturday vs Thursday mailing

0.55

0.25, 1.23

Pooled

1.07

0.33, 3.50

Type of mailing

Pedrana et al., 2008 [44]

Registered mail vs standard mail

2.97

2.31, 3.81