A slideshow adapted from what I presented in the annual conference of the European Health Psychology Society. Features a persuasive communication experiment in the context of health behavior measurement.
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⢠Physical activity recommendations based on self-
reported activity levels â problems:
⢠Remembering past activity
⢠Reporting âwhat the researcher wants to hearâ
⢠Solution: objective measurement devices
⢠New problem: need to wear it for most of the study
period!
â E.g. if you only wear the activity device when exercising,
looks like 100% of your day was spent working out!
4.5.2016 3
The âwhyâ
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The âwhyâ
⢠Letâs Move It
â A school-based multilevel intervention to
increase physical activity and decrease
sitting among youth*
â Ongoing since 2012
â RCT phase from 2015 to 2017
â Ca. 16â19 year-old vocational school
students
â Waist-worn accelerometers used
*Hankonen, Heino et al. (in preparation). Randomised controlled
feasibility study of a school-based multi-level intervention to increase
physical activity and decrease sedentary behaviour among older
adolescents.
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The Pervasive Problem:
non-wear in accelerometry
⢠Letâs Move It Feasibility study
⢠Students fell short of accelerometer wear
targets (>10hrs of data on >4 days)
â Qualitative work: non-wear attributed to
forgetting
How do we ensure adequate
accelerometer wear times?
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The setup
⢠Within-trial RCT during internal pilot study of the
main trial
⢠Participants wear the accelerometer for seven
consecutive days during Letâs Move It baseline data
collection
⢠Fight forgetting with (SMS) reminders
⢠Next question: What kind of reminders?
Could an old
copy machine
help here?
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Langer, Blank and Chanowitz (1978)
Mixed success w/ replication: Folkes (1987);
Key, Edlund, Sagarin and Bizer (2009)
âHarnessing the power of
âBecauseâââŚ?
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Message types: an example
âReasonâ, day 3:âSuccinctâ, day 3:
âHello! Because the study
wouldn't succeed without
your help, please
remember to put on the
motion measurement device
again and wear it until you
go to sleep (except in the
shower etc.) - thanks!â
[emphasis added]
âHello! Please remember to
put on the motion
measurement device again
and wear it until you go to
sleep (except in the shower
etc.) - thanks!â
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Consenting in Letâs
Move It
accelerometry
N=375
Opting in
SMS n=276
Randomised to
âReasonâ
n=138
Randomised to
âSuccinctâ
n=135
Send failed
n=7
Opting out
n=95
Participants:
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⢠Does providing a reason via SMS influence
accelerometer wear time:
â Total wear time
â Number of days >10 hours of data accumulated (0-7)
4.5.2016 11
Research questions
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⢠âProbability of observed (or rarer) data, if null
hypothesis is trueâ
⢠(also assumes randomisation, stopping rules etcâŚ)
4.5.2016 12
Whatâs a âp-valueâ again?
When p is high
(eg. p=0.32), no
conclusions can
be drawn!
(Dienes, 2014)
Reactions upon
discovering this
can vary.
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⢠remember, p-value: Probability of data, given H0
⢠A Bayes factor BF01:
Pr(đđđĄđ đđđŁđđ đť0)
Pr(đđđĄđ đđđŁđđ đť1)
4.5.2016 13
A better question?
âWhich is more probable, null or alternative?
0 âŚâ1 31/3
Very roughly:
BF01:
Data favor
alternative
Insufficient data Data favor null
A great explanation: http://alexanderetz.com/2015/11/01/evidence-vs-conclusions/
When
1
10
< BF < 10, evidence quite weak
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Measurement days of >10 hours
of valid data
Horizontal lines represent means, with shaded 95% Bayesian Highest Density Intervals (HDIs)
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Conclusions
⢠Why didnât reasons help?
⢠Hidden moderators blah blah?
⢠SMS format hinders the effect? (Why?)
⢠Wearing the device a question of capability, not
motivation?
⢠No use reasoning with adolescents?
â E.g. university students more compliant
⢠A case of an undead theory?
â Ferguson, C. J., & Heene, M. (2012). A Vast Graveyard of Undead Theories.
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Conclusions
⢠Why didnât reminders help?
⢠Operationalisation failure?
â Messages claimed to have been read but no objective log
data
⢠Self selection?
â Unlikely, as opting in was mostly determined by recruitment
prompt
⢠Non-wear not due to remembering?
â Although they said it was and thought the reminder helped
immensely!
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The Lakatos principle:
Meehl, P. E. (1990). Appraising and amending theories: The strategy of Lakatosian
defense and two principles that warrant it. Psychological Inquiry, 1(2), 108â141.
âAccepting the neo-Popperian view that it is inadvisable to persist
in defending a theory against apparent falsifications [âŚ] the
rationale for defending by non-ad hoc adjustments lies in the
theory having accumulated credit by strong successes, having lots
of money in the bank.â â Paul Meehl
- Does the âpower of becauseâ lean on Monopoly money?