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Sample Size Determination
Sample size was estimated by using the following formula described by Browener, Newman,
Cummings and Hulley (2001).
2 (Z α +Z β) 2 ϭ2
N=
e2
According to the study done by Naveed et al., (2010),
Mean1 µ1= Mean HOMA IR value in premenopausal women = 4.23
Mean 2 µ2 = Mean HOMA IR value in postmenopausal women = 2.89
SD1= standard deviation of HOMA IR value in premenopausal women =2.36
SD2 = standard deviation of HOMA IR value in premenopausal women = 1
Ϭ= 3.2848
e = effect size (µ1- µ2)- 1.34
Z α = standard normal deviation for α = Z α= 1.96
Z β = standard normal deviation for β = Z β = 0.84
N = 29
The acceptable minimal sample size is 29.
References
1. Browener WS, Newman TB, Cummings SR and Hulley SB. (2001) The Nitty-gritty. In: Hulley,
S.B., Cummings, S.R., Browener, W.S., Grady, D., Hearst, N. and Newman, T.B. (Eds),
Designing Clinical Research: An epidemiologic approach. 2nd ed. Philadelphia: Lippincott
Willams and Wilkins, 65-94.
2. Naveed AK,Raiput TA and Mahmood N. Effect of Variations in Body Mass Index on
Serum Leptin Levels in Pre and Post Menopausal Women. Global Journal of Health
Science. 2010;2(1):178-192.