Slovin Formula
SAMPLE AND SAMPLING TECHNIQUE
Sample ▪ 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__ ▪ 1+NE² ▪ 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__ 1+NE² n = 10,000 = 2,000
Sample ▪ 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__ ▪ 1+NE² ▪ 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__ 1+NE² n = 10,000 = 2,000