Characteristics of Samples Used for Quantitative Analyses in the Journal Body Image

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# Characteristics of Samples Used for Quantitative Analyses in the Journal Body Image
### Thomas Pollet, et al. <br> Northumbria University <br><br> (<a href="mailto:thomas.pollet@northumbria.ac.uk" class="email">thomas.pollet@northumbria.ac.uk</a>)
### 2024-03-03 | <a href="http://tvpollet.github.io/disclaimer">disclaimer</a>

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## Samples in psychology

* Describing the samples we use.

--> Recurrent criticism that psychology relies on student samples (e.g., [Thalmayer et al. 2020](https://doi.org/10.1037/amp0000622))

--> [W.E.I.R.D.](https://www2.psych.ubc.ca/~henrich/pdfs/WeirdPeople.pdf) : Western Educated Industrialised Rich and Democratic

Previous project on samples used in [Evolution and Human Behaviour and Evolutionary Psychology](https://link.springer.com/article/10.1007/s40806-019-00192-2).

???
70% Online or student samples / >80% from 'Western' countries (Europe, USA/CAN/AUS)

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## Sampling

A closer look at the samples being used in _Body Image_

Descriptive project

* Are samples different from general population in terms of BMI?

???
Why focus on age and BMI. Interesting variables: Aging population / population becoming more obese.
Separate gen. pop. and students.

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## Methodology.

* All papers from 2021 from _Body Image_ (_n_ = 137).

* 149 samples (5 meta-analyses or content analyses not analysed further).

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## Methodology: Simulations

* **BMI**. Overall population estimate by gender from [NCD Risk Factor Collaboration (NCD-RisC)](https://linkinghub.elsevier.com/retrieve/pii/S0140673617321293) from 2016. Further checks with matched age groups.

* 100k simulations. One simulation: Draw a random sample (_n_) of the same size as the original study's sample size. `\(n \sim \mathcal{N}(\mu,\,\sigma^{2})\)` using the Means and SD provided. We then perform a one sample _t_-test against the reference value.

* median _p_ value of those 100k simulations.

???
Also completed age sims.

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## Map: Inclusion.

???
Some coverage of Latin America, no coverage of Africa, China, Russia
Majority of quantitative samples are from the United States (n = 55), followed by the United Kingdom (n = 18), Australia (n = 18) and Canada (n = 11).

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## Map: k samples.

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## Map: Total sample sizes.

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## Map: Median sample size.

???
Large sample from New Zealand. (AUS: 230; USA: 317; UK: 271.5; NZL: 6258)

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## Type of samples

???
pregnant women (n = 1), mothers (n = 1) and a sample of students but who scored in the top tertile on a sub-scale of the EDI-2. Only four samples labelled as clinical. One gen. pop. sample recruited via churches.

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class: simulation
## Simulations: BMI (general population)

<table style="text-align:center"><caption><strong>Summary of simulations. Note: p < .1 = ., p < .05 = *, p < .01 = **, p < .001 = ***.</strong></caption>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr><tr><td style="text-align:left">Country</td><td>Gender of sample</td><td>Mean BMI</td><td>SD BMI</td><td>Sample Size</td><td>Mean BMI population</td><td>p</td></tr>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr><tr><td style="text-align:left">USA</td><td>Female</td><td>26.71</td><td>7.69</td><td>350</td><td>29.07</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>28.20</td><td>7.97</td><td>135</td><td>29.07</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>28.58</td><td>7.36</td><td>126</td><td>29.07</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>26.70</td><td>6.50</td><td>82</td><td>29.07</td><td>* *</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>27.18</td><td>8.85</td><td>115</td><td>29.07</td><td>*</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>27.82</td><td>7.31</td><td>130</td><td>29.07</td><td>.</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>28.99</td><td>7.44</td><td>132</td><td>29.07</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>27.01</td><td>6.41</td><td>13</td><td>29.07</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Male</td><td>25.33</td><td>6.23</td><td>1,011</td><td>29.01</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Male</td><td>28.47</td><td>7.83</td><td>153</td><td>29.01</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Male</td><td>28.60</td><td>5.34</td><td>108</td><td>29.01</td><td></td></tr>
<tr><td style="text-align:left">UK</td><td>Female</td><td>26.99</td><td>8</td><td>188</td><td>27.15</td><td></td></tr>
<tr><td style="text-align:left">UK</td><td>Male</td><td>24.41</td><td>3.52</td><td>42</td><td>27.48</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>23.50</td><td>5.34</td><td>227</td><td>26.87</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>27.85</td><td>7.85</td><td>240</td><td>26.87</td><td>.</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>24.59</td><td>5.43</td><td>291</td><td>26.87</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>28.35</td><td>6.91</td><td>206</td><td>26.87</td><td>* *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>24.71</td><td>5.60</td><td>119</td><td>26.87</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>25.90</td><td>6.42</td><td>3,039</td><td>26.87</td><td>* * *</td></tr>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr></table>

---
class: simulation
## Simulations: BMI (Students)

<table style="text-align:center"><caption><strong>Summary of simulations. Note: p < .1 = ., p < .05 = *, p < .01 = **, p < .001 = ***.</strong></caption>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr><tr><td style="text-align:left">Country</td><td>Gender of sample</td><td>Mean BMI</td><td>SD BMI</td><td>Sample Size</td><td>Mean BMI population (20-24)</td><td>p</td></tr>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr><tr><td style="text-align:left">USA</td><td>Female</td><td>25.57</td><td>7.39</td><td>371</td><td>26</td><td></td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>24.89</td><td>6</td><td>475</td><td>26</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>23.67</td><td>4.46</td><td>151</td><td>26</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>22.25</td><td>3.17</td><td>556</td><td>26</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Female</td><td>23.11</td><td>3.54</td><td>349</td><td>26</td><td>* * *</td></tr>
<tr><td style="text-align:left">USA</td><td>Male</td><td>25.44</td><td>5.09</td><td>265</td><td>26.74</td><td>* * *</td></tr>
<tr><td style="text-align:left">UK</td><td>Female</td><td>23.61</td><td>4.97</td><td>189</td><td>24.76</td><td>* *</td></tr>
<tr><td style="text-align:left">UK</td><td>Female</td><td>24.24</td><td>3.99</td><td>51</td><td>24.76</td><td></td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>22.10</td><td>3.70</td><td>373</td><td>24.29</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>21.50</td><td>3</td><td>115</td><td>24.29</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>21.74</td><td>3.71</td><td>146</td><td>24.29</td><td>* * *</td></tr>
<tr><td style="text-align:left">AUS</td><td>Female</td><td>24.82</td><td>5.67</td><td>233</td><td>24.29</td><td></td></tr>
<tr><td style="text-align:left">AUS</td><td>Male</td><td>23.89</td><td>4.81</td><td>66</td><td>25.38</td><td>*</td></tr>
<tr><td style="text-align:left">CAN</td><td>Female</td><td>21.83</td><td>4.97</td><td>142</td><td>24.10</td><td>* * *</td></tr>
<tr><td style="text-align:left">CAN</td><td>Female</td><td>22.83</td><td>3.73</td><td>24</td><td>24.10</td><td></td></tr>
<tr><td style="text-align:left">CAN</td><td>Female</td><td>22.89</td><td>4.28</td><td>28</td><td>24.10</td><td></td></tr>
<tr><td style="text-align:left">CAN</td><td>Female</td><td>23.35</td><td>4.34</td><td>340</td><td>24.10</td><td>* *</td></tr>
<tr><td style="text-align:left">CAN</td><td>Female</td><td>23.25</td><td>4.90</td><td>311</td><td>24.10</td><td>* *</td></tr>
<tr><td colspan="7" style="border-bottom: 1px solid black"></td></tr></table>

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## Summary

* Provided an overview of the type of samples that are in _Body image_ .

* Simulations suggest that "general population" samples tend to differ from the overall population in age and sometimes also BMI.

* Simulations suggest that student samples tend to differ from age matched population samples in BMI.

???
Limitations: descriptive project. Did not code claims on inference or generality. Though some examples call for further research on other cultures or ethnicities.

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## Any Questions?

[Preprint](https://osf.io/preprints/psyarxiv/2qfdb) ; [Longer talk](https://tvpollet.github.io/Talk_appearance_Durham_22/Talk_Durham_Body_Image_22.html#1)

[http://tvpollet.github.io](http://tvpollet.github.io)

X/Twitter: @tvpollet ; Bluesky: @tvpollet.bsky.social

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## Acknowledgments

* I am greatly indebted to my collaborators (Jeanne Bovet, Rosie Buhaenko, Piers Cornelissen, Martin Tovée). (Any mistakes are my own!).

* You for listening!