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How we are misinterpreting physical activity intention - behavior relations and what to do about it

journal contribution
posted on 30.01.2020, 00:00 by Amanda RebarAmanda Rebar, RE Rhodes, B Gardner
Background: Studies of the physical activity intention-behavior gap, and factors that may moderate the gap (e.g., habit, perceived behavioral control), can inform physical activity promotion efforts. Yet, these studies typically apply linear modeling procedures, and so conclusions rely on linearity and homoscedasticity assumptions, which may not hold. Methods: We modelled and plotted physical activity intention-behavior associations and the moderation effects of habit using simulated data based on (a) normal distributions with no shared variance, (b) correlated parameters with normal distribution, and (c) realistically correlated and non-normally distributed parameters. Results: In the uncorrelated and correlated normal distribution datasets, no violations were unmet, and the moderation effects applied across the entire data range. However, because in the realistic dataset, few people who engaged in physical activity behavior had low intention scores, the intention-behavior association was non-linear, resulting in inflated linear moderation estimations of habit. This finding was replicated when tested with intention-behavior moderation of perceived behavioral control. Conclusions: Comparisons of the three scenarios illustrated how an identical correlation coefficient may mask different types of intention-behavior association and moderation effects. These findings highlight the risk of misinterpreting tests of the intention-behavior gap and its moderators for physical activity due to unfounded statistical assumptions. The previously well-documented moderating effects of habit, whereby the impact of intention on behavior weakens as habit strength increases, may be based on statistical byproducts of unmet model assumptions. © 2019 The Author(s).

Funding

Category 1 - Australian Competitive Grants (this includes ARC, NHMRC)

History

Volume

16

Start Page

1

End Page

13

Number of Pages

13

eISSN

1479-5868

Publisher

BioMed Central, UK

Additional Rights

CC BY 4.0

Peer Reviewed

Yes

Open Access

Yes

External Author Affiliations

University of Victoria, Canada; King’s College London, UK

Author Research Institute

Appleton Institute

Era Eligible

Yes

Journal

International Journal of Behavioral Nutrition and Physical Activity

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