Slovin Formula

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▪ Is a finite number of an item (or individual) taken from a population having identical characteristics with those of the population from which it was taken. ▪ A sample is considered biased if one or several of the items (or individuals) in the population are given a consistently better opportunity to be chosen than the others. ▪ A collection with specified dimension

Sample size
▪ Random sampling, the larger the sample, the more accurately it represents the population from which it was taken. ▪ As the sample size decreases, the degree of representativeness becomes less. Size of sample depends on some factors:

▪ Degree of accuracy required
▪ Amount of variability inherent in the population from which the sample was taken ▪ Nature and complexity of the characteristics of the population under consideration

Sample Strategy
▪ Common Misguided Approach
▪ decide what data to collect
▪ then undertake survey
▪ decide what analysis should be done
▪ wrong data collected
▪ data collected on wrong subjects
▪ insufficient data collected
▪ Desired analysis may not be possible or effective

Key to Good Sampling
▪ formulate the aims of the study
▪ decide what analysis is required to satisfy this aims ▪ decide what data are required to facilitate the analysis ▪ collect the data required by the study

Determine sample size
▪ Slovin Formula:
n = N__
▪ Where: n = sample size
N = population size
E = margin of error * desired

Example:What should be the representative sample size if the population from which the sample will be taken is 10,000 and the desired margin of error is 2%? Solution:To determine the sample size, use the formula; n = ___N__

n = 10,000 = 2,000
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