2.6 SAMPLE SIZE ESTIMATION
The sample size for the study was determined by Fischer’s formula using the prevalence rate of 75% found in a study in Nigeria by Morhason-Bello et al . 13
n = p (1-p)z2/d2
where n = sample size, z = Z-score, d = desired error margin and p = prevalence.
Using a prevalence of 75% and 95% confidence interval, d = 0.05, Z = 1.96, p = 0.75
Therefore, n = 0.75(1-0.75) x 1.962/ 0.052
= 288.
The population size (N) is less than 10,000 (3300).
Therefore, we calculated the desired sample size (nf) was calculated as nf = n/1+n/N
= 288 / 1 + 288/3300 = 288/1 + 0.087 = 288/1.087
= 265.
We added a 10% attrition rate of (27).
Thus, the total sample size will be a minimum of 292 respondents for the study.