Jun 1, 2010

Krejcie and Morgan (Method for determining sample size of a population)

For any research, the sample size of any study must be determined during the designing stage of the study. However, before determining the size of the sample that needed to be drawn from the population, a few factors must be taken into consideration. According to Salant and Dillman (1994), the size of the sample is determined by four factors: (1) how much sampling error can be tolerated; (2) population size; (3) how varied the population is with respect to the characteristics of interest; and (4) the smallest subgroup within the sample for which estimates are needed.

Using the above methods as a guideline, the following section aims to compare two approaches in determining the sample size of a population of 500 people using (a) Krejcie and Morgan (1970) and (b) Cohen Statistical Power Analysis. In this article i wanna explain about Krejcie and morgan method.

Estimation of sample size in research using Krejcie and Morgan is a commonly employed method. Krejcie and Morgan (1970) used the following formula to determine sampling size:
S = X2NP (1-P)/ d2 (N-1) + X2P(1-P)
S = required sample size
X2 = the table value of chi-square for one degree of freedom at the desired
confidence level
N = the population size
P = the population proportion (assumed to be .50 since this would
provide the maximum sample size)
d = the degree of accuracy expressed as a proportion (.05)

Based on Krejcie and Morgan’s (1970) table for determining sample size, for a given population of 500, a sample size of 217 would be needed to represent a crosssection of the population. However, it is important for a researcher to consider whether the sample size is adequate to provide enough accuracy to base decisions on the findings with confidence. Therefore, in order to find out if the sample size recommended by Krejcie and Morgan (1970) is sufficient, the next section aims to illustrate the estimation of sampling size using Cohen’s (1988) statistical power analysis.

@Source : Chua Lee Chuan journal

1 comment:

TUKANG CoLoNG said...

google translate..:)

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