There are various sample size estimation formulas that are published in literature but has no adequate mathematical and statistical background. Many of such formula often assumed normal distribution that becomes unreliable most especially when observations are few. This study thus, established sample size estimation formula from generalized exponential power distribution (GEPD) which has normal, Laplace and uniform distribution has its members. We employed an approximation to the incomplete gamma cumulative distribution function of the GEPD via series expansion to obtain the pivotal quantity from which the sample size of GEPD was derived. Application to sample size calculation from Likert scaled questionnaire was demonstrated.
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