. Author manuscript; available in PMC: 2017 May 5.

Published in final edited form as: J Res Educ Eff. 2015 Nov 23;9(4):556–569. doi: 10.1080/19345747.2015.1086916

Table 3.

Scenarios 1 & 2: Manipulating Participant Selection - Statistical Power at Different Cut Points

		Direct Range Restriction				Indirect Range Restriction

Cut Point	N^a	Pretest- Posttest r	MDES^b	Participants Needed^c	Estimated Power^d	Pretest- Posttest r	MDES^b	Participants Needed^c	Observed Power^d
No Cut Point	100,000	.85	.21	142	.80	.85	.21	142	.80
< 0	49,915	.70–.70	.28–.29	258–262	.54–.55	.77–.80	.24–.25	186–212	.63–.69
< −.33 SD	37,005	.66–.67	.30–.30	284–286	.51–.51	.75–.79	.24–.26	190–222	.61–.68
< −.5 SD	30,860	.64–65	.30–.30	294–298	.49–.49	.74–.79	.25–.27	194–228	.60–.67
< −.67 SD	25,061	.62–.63	.31–.31	306–312	.47–.48	.74–.78	.25–.27	198–230	.59–.66
< −.75 SD	22,564	.61–62	.31–.32	312–318	.46–.47	.74–.78	.25–.27	198–230	.59–.66
< −1 SD	15,815	.58–.60	.32–.32	324–336	.44–.46	.73–.78	.25–.27	202–236	.58–.65
< −1.25 SD	10,569	.56–.57	.33-.33	340–346	.43–.44	.73–.78	.25–.27	202–240	.58–.65
< −1.5 SD	6,666	.53–56	.33–.34	350–362	.42–.43	.72–.77	.25–.27	204–242	.57–.65

N is the mean number of observations simulated for the both upper and lower limit parameters;

Calculated at p < .05, N = 200; power = .80;

Calculated at p < .05, d = .25, power = .80.

Calculated at p < .05, d = .25, N =142;

Note: Bold = Baseline scenario (Scenario 1); Test 1–Test 2 r = .75; pretest - posttest r = .85 (both Test 1 and Test 2); Test 1 pretest - Test 2 posttest r = .61 – .75.