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Conversion between some effect sizes

Conversion between some effect sizes
Conversion between some effect sizes

Perugini, M., et al. (2018). A Practical Primer To Power Analysis for Simple Experimental Designs. International Review of Social Psychology, 31(1): 20, 1–23, DOI: https://doi.org/10.5334/irsp.181

Design

3x2 ANOVA (3 between x 2 between)

Factors: SES origin (poor-middle-rich) x Crime (shoplifting-vandalism). Six groups.

G*Power

G*Power settings:

  • Test family: F tests
  • Statistical test: ANOVA Fixed effects, special, main effects and interactions
  • Numerator df (n-1)(k-1): 2
  • Number of groups: 6
  • Power: 0.9
Cohen’s f Total Sample Size
0.25 206
0.20 320
0.15 566
0.10 1269
  • Power: 0.85
Cohen’s f Total Sample Size
0.25 178
0.20 277
0.15 489
0.10 1096
  • Power: 0.80
Cohen’s f Total Sample Size
0.25 158
0.20 244
0.15 432
0.10 967

Mediation

Using https://schoemanna.shinyapps.io/mc_power_med/ Schoemann’s online tool for a Monte Carlo power analysis with 20,000 samples for a simple mediation model. Since our model involves multicategorical mediation with three groups in the antecedent variable, we multiply the sample size by 1.5 .

Input parameters:

  • The correlation between conditions and mediator (a path), as well as between mediator and outcome (b path), is expected to be medium-sized (r=.24)
  • The correlation between conditions and outcome (c’ path) is expected to be small (r=.1).
Power Sample size (2 groups) Sample size (3 groups)
0.80 195 293
0.85 215 323
0.90 240 360
0.95 280 420
  • The correlation between conditions and mediator (a path), as well as between mediator and outcome (b path), is expected to be medium-sized (r=.3)
  • The correlation between conditions and outcome (c’ path) is expected to be small (r=.1).
Power Sample size (2 groups) Sample size (3 groups)
0.80 125 188
0.85 135 203
0.90 145 218
0.95 165 248

Preregistration statement

Based on prior research and power analyses, we aim to collect usable data from 240 participants. To deal with possible casewise exclusions based on failure to respond correctly to an attention check question, we will add 10% to this number and collect a total of ~264 cases.