Table 4. Overview of risk of biases for each individual study.
| Author | Year | Sources of potential biases | Potential biases | Mechanisms to counter biases | Rating of risk of bias |
|---|---|---|---|---|---|
| Gan & Chong [79] | 2015 | Cross-sectional design | Common method variance | None employed | High risk |
| Self-report | Sampling bias | ||||
| 57% response rate—no differential analysis of dropouts | Social desirability bias | ||||
| Attrition bias | |||||
| Sonesh, Coultas, Marlow, Lacerenza, Reyes & Salas [55] | 2015 | Cross-sectional design | Common method variance | Self-report data from coach and coachee | High risk |
| Self-report | Sampling bias | ||||
| Social desirability bias | |||||
| Biggs, Brough & Barbour [68] | 2014 | Nonrandomised group allocation—pre-existing differences between groups | Selection bias | Control group | Low risk |
| No differential analysis of dropouts | Attrition bias | Other-raters | |||
| Pre & post assessment | |||||
| Hoven, Ford, Willmot, Hagan & Siegrist [44] | 2014 | Nonrandomised group allocation | Selection bias | Control group | Low risk |
| Objective outcome | |||||
| Longitudinal outcome | |||||
| Ladegard & Gjerde [49] | 2014 | Small sample size | Selection bias | Control Group | Low risk |
| Nonrandomised group allocation | Attrition bias | Other-raters | |||
| 73% response rate—no differential analysis of dropouts | Pre & post assessment | ||||
| Jones, Woods & Hutchinson [70] | 2014 | Small sample size | Common method variance | None employed | High risk |
| Cross-sectional design | Social desirability bias | ||||
| Self-report | Sampling bias | ||||
| Gatling & Harrah [77] | 2014 | Cross-sectional design | Common method variance | None employed | High risk |
| Self-report | Social desirability bias | ||||
| Sampling bias | |||||
| Grant [57] | 2014 | Small sample size | Common method variance | Pre & post assessment | Medium risk |
| Self-report | Social desirability bias | ||||
| Sampling bias | |||||
| Mackie [46] | 2014 | Small sample size | Selection bias | Control group | Low risk |
| Nonrandomised group allocation | Multiple raters | ||||
| Pre & post assessment | |||||
| Longitudinal assessment | |||||
| ANCOVA | |||||
| Analysis of rater consistency | |||||
| O’Connor & Cavanagh [54] | 2013 | Small sample size | Selection bias | Control group | Low risk |
| Multiple raters | |||||
| Pre & post assessment | |||||
| Ianiro, Schermuly & Kauffeld [47] | 2013 | Small sample size | Sampling bias | Other-raters | Medium risk |
| Self-report coaching success | Social desirability bias | Pre & post assessment | |||
| Smith & Brummel [63] | 2013 | Small sample size | Common method variance | Experts coded responses | High risk |
| Cross-sectional design | Sampling bias | ||||
| Self-report | Social desirability bias | ||||
| De Haan, Duckworth, Birch & Jones [29] | 2013 | Cross-sectional design | Common method variance | Self-report data from coach and coachee | High risk |
| Self-report | Sampling bias | ||||
| Social desirability bias | |||||
| Grant [31] | 2013 | Small sample size | Common method variance | Pre and post assessment | Medium risk |
| Self-report | Sampling bias | ||||
| No differential analysis of dropouts | Social desirability bias | ||||
| Attrition bias | |||||
| Nieminen, Smerek, Kotrba & Denison [66] | 2013 | Nonrandomised group allocation—pre-existing differences between groups | Selection bias | Control group | Low risk |
| Multiple raters | |||||
| Pre and post assessment | |||||
| Bozer & Sarros [60]; Bozer, Sarros & Santora[75]; Bozer, Sarros & Santora [74]; Bozer, Joo & Santora [80] | 2012; 2013; 2014; 2015 | Nonrandomised group allocation | Selection bias | Control group | Low risk |
| Supervisor ratings | |||||
| Pre and post assessment | |||||
| Vidal-Salazar, Ferrón-Vilchez and Cordón-Pozo [69] | 2012 | Small sample size | Selection bias | Control group | Medium risk |
| Cross-sectional design | Other-raters | ||||
| Nonrandomised group allocation | |||||
| Bright & Crockett [62] | 2012 | Pre-existing differences between groups | Selection bias | Control group | Medium risk |
| Self-report | Social desirability bias | Randomised group allocation | |||
| New measure utilised—no validity or reliability information given | Measurement bias | Pre and post assessment | |||
| Blackman & Moscardo [42] | 2012 | Cross-sectional design | Common method variance | None employed | High risk |
| Self-report | Social desirability bias | ||||
| Sampling bias | |||||
| Crompton [39] | 2012 | Cross-sectional design | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Objective outcome measure | |||
| Sampling bias | Structural Equation Modelling | ||||
| Ladegård [45] | 2011 | Self-report | Social desirability bias | Pre & post assessment | Medium risk |
| 50% response rate | Attrition bias | Longitudinal assessment | |||
| New measure utilised—no validity or reliability information given | Measurement bias | Differential analysis of dropouts | |||
| De Haan, Culpin & Curd [73] | 2011 | Small sample size | Common method variance | Pre and post assessment | Medium risk |
| Self-report | Sampling bias | ||||
| 28% response rate—no differential analysis of dropouts | Social desirability bias | ||||
| Attrition bias | |||||
| Scriffignano [76] | 2011 | Cross-sectional design | Common method variance | None employed | High risk |
| Self-report | Social desirability bias | ||||
| 67% response rate—no differential analysis of dropouts | Sampling bias | ||||
| Attrition bias | |||||
| Richardson [41] | 2010 | Small sample size | Selection bias | Control group | Low risk |
| Nonrandomised group allocation | Other-raters | ||||
| Pre and post assessment | |||||
| Kochanowski, Seifert & Yukl [67] | 2010 | Small sample size | Selection bias | Control group | Low risk |
| No differential analysis of dropouts | Attrition bias | Other-raters | |||
| Pre and post assessment | |||||
| Leonard-Cross [4] | 2010 | Cross-sectional design | Common method variance | Control group | High risk |
| Self-report | Sampling bias | ||||
| Nonrandomised group allocation | Social desirability bias | ||||
| Cerni, Curtis & Colmar [65] | 2010 | Small sample size | Selection bias | Control group | Low risk |
| Nonrandomised group allocation | Multiple raters | ||||
| Pre and post assessment | |||||
| Grant, Green & Rynsaardt [53] | 2010 | Small sample size | Selection bias | Control group* | Medium risk |
| Self-report* | Attrition bias | Multiple raters* | |||
| Multirater feedback provided to only coached group | Confounding bias | Pre and post assessment | |||
| No differential analysis of dropouts | |||||
| Grant, Curtayne & Burton [52] | 2009 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Pre and post assessment | |||
| No differential analysis of dropouts | Selection bias | ||||
| Attrition bias | |||||
| Baron & Morin [27]; Baron, Morin & Morin [78] | 2009; 2011 | Self-report for outcome measure | Common method variance | Self-report data from coach and coachee | Medium risk |
| 58% response rate—no differential analysis of dropouts | Social desirability bias | Pre and post assessment | |||
| Selection bias | |||||
| Attrition bias | |||||
| Perkins [48] | 2009 | Small sample size | Sampling bias | Coach/author coded meeting behaviours | Medium risk |
| New measure utilised—some validity and reliability information given | Measurement bias | Pre and post assessment | |||
| Moen & Skaalvik [97]; Moen & Federici [98]; Moen & Federici [50] | 2009; 2012; 2012 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Randomised group allocation | |||
| New measures utilised—no validity or reliability information given | Selection bias | Pre and post assessment | |||
| Measurement bias | |||||
| Stewart, Palmer, Wilkin & Kerrin [72] | 2008 | Cross-sectional design | Common method variance | None employed | High risk |
| Self-report | Social desirability bias | ||||
| New measures utilised—some validity or reliability information given | Sampling bias | ||||
| Measurement bias | |||||
| Yu, Collins, Cavanagh, White & Fairbrother [56] | 2008 | Small sample size | Common method variance | Pre and post assessment | Medium risk |
| Self-report | Social desirability bias | ||||
| No differential analysis of dropouts | Sampling bias | ||||
| Attrition bias | |||||
| Finn (Study 1) [40] | 2007 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Random group allocation | |||
| New measures utilised—some validity or reliability information given | Selection bias | Pre and post assessment | |||
| Attrition bias | Longitudinal assessment | ||||
| Differential analysis of dropouts | |||||
| Finn (Study 2) [40] | 2007 | Small sample size | Selection bias | Control group | Low risk |
| New measures utilised—some validity or reliability information given | Attrition bias | Random group allocation | |||
| Multiple raters | |||||
| Pre and post assessment | |||||
| Longitudinal assessment | |||||
| Differential analysis of dropouts | |||||
| Bowles, Cunningham, De La Rosa & Picano [61] | 2007 | Small sample size | Sampling bias | Other-raters | Medium risk |
| Pre and post assessment | |||||
| Orenstein [99] | 2006 | Small sample size | Sampling bias | Other-raters | High risk |
| Cross-sectional design | Measurement bias | ||||
| New measure utilised—no validity or reliability information given | |||||
| Evers, Brouwers & Tomic [51] | 2006 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Pre and post assessment | |||
| New measure utilised—no validity or reliability information given | Sampling bias | ||||
| Pre-existing differences between groups | Measurement bias | ||||
| Scoular & Linely [71] | 2006 | Cross-sectional design | Common method variance | Self-report data from coach and coachee | High risk |
| Self-report | Social desirability bias | ||||
| Sampling bias | |||||
| Jones, Rafferty & Griffin [64] | 2006 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Pre and post assessment | |||
| Several participants attend a course during the intervention | Sampling bias | ||||
| Confounding bias | |||||
| Toegel & Nicholson [43] | 2005 | Self-report | Common method variance | Multiple raters | Medium risk |
| 60% response rate—no differential analysis of dropouts | Social desirability bias | Pre and post assessment | |||
| Sampling bias | |||||
| Attrition bias | |||||
| Gyllensten & Palmer [58] | 2005 | Small sample size | Common method variance | Control group | Medium risk |
| Self-report | Social desirability bias | Pre and post assessment | |||
| Nonrandomised group allocation | Sampling bias | ||||
| Gyllensten & Palmer [59] | 2005 | Cross-sectional design | Common method variance | Control group | High risk |
| Self-report | Social desirability bias | ||||
| Nonrandomised group allocation | Sampling bias | ||||
| Smither, London, Flautt, Vargas & Kucine [16] | 2003 | Nonrandomised group allocation | Selection bias | Control group | Low risk |
| Multiple raters | |||||
| Pre and post assessment | |||||
| Luthans & Peterson [15] | 2003 | Small sample size | Sampling bias | Multiple raters | Medium risk |
| Pre and post assessment |
Note:
*not used for all outcome measures.