mankarious evon 20130208
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Evon MankariousEmily Kothe
Measurement Reactivity
A Meta-Analysis of the Effects of Presenting Theory of Planned Behaviour Constructs on
Follow-Up Behaviour
Outline of presentation
2
• Introduction-What is measurement reactivity and why does it occur?
• Methods
-Inclusion and Exclusion criteria
-Database search and search terms
-Data-extraction and meta-analytical process
• Results
-Literature search
-Number of studies included
-Number of studies measuring particular behaviours
-Moderator analyses and sub-group analyses
• Discussion
-What do the results suggest?
-Strengths and limitations
-Future direction
What is measurement reactivity and why does it occur?
3
• Phenomenon occurs when the mere presentation of questions about intention at baseline changes follow-up behaviour
• Likely to occur in any theory where intention is a central construct- Theory of planned behaviour was used here.
Theory of planned behaviour
4
Measurement reactivity changes in behaviour at follow-up
• Measurement reactivity has been reported to change follow-up behaviour in many health behaviours:
- Cervical cancer screening (Sandberg and Conner, 2009)
- Blood donation (Godin et al., 2008)
- Physical activity (Godin et al., 2011)
- Illicit drug use (Williams et al., 2006)
5
Limitations of measurement reactivity literature
6
Measurement reactivity
Participation effects
Behavioural change
Problems with isolating measurement reactivity from participation effects
• Kypri et al. (2011) – What participants think about the nature of the study may affect subsequent behaviour and potentially bias study findings
• doesn’t address the issue of measurement reactivity as measurement of intention remains common across all groups.
• Solomon four-group designs can experimentally manipulate baseline assessment but do not isolate measurement reactivity from participation effects.
7
Significance of the current analysis and aims
• Best way- investigate changes in non-intervention studies which measure intention at baseline and behaviour at both baseline and follow-up through meta-analytical techniques.
• Using studies not designed to investigate measurement reactivity reduces risk of potential publication bias in measurement reactivity literature.
• No research has attempted to systematically investigate the existence of measurement reactivity within non-intervention studies.
8
Aims
to determine the extent to which behaviour changed in non-intervention studies which applied the theory of planned behaviour questionnaire to measure intention at baseline.
9
Investigation of Moderator Variables
• Type of behaviour (Socially desirable vs. undesirable)
- inconsistencies in measurement reactivity studies measuring socially undesirable behaviour.
- Included to determine if classification of behaviour had a moderating effect
• Length of follow-up
- Based on previous literature, was hypothesised that increasing length of follow-up time would decrease magnitude of measurement reactivity.
10
Inclusion/Exclusion criteria
11
Inclusion Exclusion
Only studies looking at health behaviours
Cross-sectional, qualitative, and intervention studies
measured all theory of planned behaviour constructs at baseline
Articles published in languages other than English
measured behaviour at baseline and follow-up
Database search and search terms
• Literature search and data extraction phases were performed in June 2012.
• PsychINFO (OVID), MEDILINE (OVID) and Web of Science (ISI web of knowledge) databases
• Search strategy used here was modelled on a recent meta-analysis on the theory of planned behaviour in prospective studies conducted by McEachan and colleagues (2011).
12
Data extraction and met-analysis procedure
• Mean, standard deviation, and sample size at both baseline and follow-up were extracted to allow for the calculation of effect sizes
• Cohen’s d was calculated to determine the standardised mean difference for behaviour from baseline to the first follow-up
• Meta-analysis conducted using the Metafor package for R
• Follow-up length of time and behaviour type examined in a mixed-effects model.
• Sub-group analyses were also conducted to determine the mean effect size for behaviour investigated in more than one study
13
Results: Literature search
14
Literature Search n
Database search (after duplicates removed) 4034
Title 1630
Abstract 2221
Full-text 183
Total 23
Number of studies measuring particular behaviours and Type of behaviour
15
Length of follow-up
Length of follow-up n
1 week 5
2 weeks 3
4 weeks 1
5 weeks 3
6 weeks 1
8 weeks 2
3 months 2
6 months 6
16
Moderator analysis, changes in behaviour across all studies and sub-group analyses
• Non-significant effects were found for behaviour type (p = .35) and for follow-up length (p = .83)
• Average change in behaviour across all studies was small (d = -.08, 95% CI [-0.17, 0.01])
• Physical Activity
- Average change from baseline to follow-up was small (k = 13, d < .001, 95% CI [-0.07, 0.07]
• Binge Drinking behaviour:
- Average change from baseline to follow-up was small and decreased (k = 2, d = -0.14, 95% CI [-0.41, 0.13]
17
Discussion: Does measurement reactivity occur?
• Results did not support a measurement reactivity account of behavioural change
• Changes in behaviour in intervention studies may actually be the result of other factors, for example participation effects and not measurement reactivity
18
Is length of follow-up time a moderator?
• No- non-significant effects were found
• Hypothesis that increasing follow-up length of time would reduce magnitude of measurement reactivity was not supported.
• Researchers using this theory should use the theory to accurately predict behaviour and it does not appear that they should be concerned about measurement reactivity.
19
• No
• Changes in behaviour in studies investigating socially desirable behaviours did not differ from studies investigating socially undesirable behaviours.
• Inconsistencies observed between studies which have measured socially undesirable behaviours may be the result of:
- Question framing
- socially undesirable behaviours may also affected by social norms
20
Does behaviour type matter?
Sub-group analyses
• Binge Drinking:
- Small decrease in behaviour
- Caution should be used as only 2 studies were found
- Previous studies have shown that presenting questions about intention at baseline can decrease binge drinking behaviour
- As only 2 studies were included, it is possible that changes in binge drinking behaviour may be the result of measurement reactivity.
• Physical Activity:
- Results suggest that changes in behaviour are unlikely to be the result of measurement reactivity and may reflect participation effects.
- Not consistent with previous research
21
Strengths and Limitations
22
Strengths Limitations
• No previous meta-analysis looking at measurement reactivity
• Use of large body of literature reduced publication bias
• Sub-group analyses could not be conducted on many behaviours
• Studies may have measured behaviour twice but reported it once
Future direction
• To increase number of studies included in future meta-analyses, other theories that have intention as a core construct could be included
• To our knowledge, no research exists which allows for the separation of behavioural change believed to be the result of measurement reactivity vs. behavioural changes as a result of participation effects.
• New design would be an 8-arm 2x2x2 fully crossed factorial design.
23
Example of new study design
24
Thank-you
25
References
26
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