3.3.3 Study design and sample size
This study was repeated cross sectional design involving collection of
rodent sample across season (wet and dry season). Preliminary survey was
conducted in a study area one week before rodent sampling begun to
request permission and inform authority about this study. Sherman live
animal traps were used to capture rodents in farm land, bush land,
peridomestic areas and forest buffer zone.
Rodent sample size was estimated with formula described by Nainget al . (2006)
\begin{equation}
n=\frac{Z^{2}\text{\ P\ }\left(1-P\right)}{d^{2}}\nonumber \\
\end{equation}Whereby n= sample size; Z= test statistics at 95% confidence level;P = expected prevalence of Yersinia pestis in rodents;
(1-p ) = probability of having no infected rodent; d =
desired level of precision. Values in the formula are: Z=1.96, d =
5% and P = 10%. By inserting the values into the formula\((\frac{\par
\begin{matrix}{1.96}^{2}&\times 0.1(1-0.1)\\
\end{matrix}}{{0.05}^{2}}\)= 138.29). Therefore, sample size for this
study was estimated to be 140 rodents in each season (wet and dry)
giving a total sample size of 280 rodents.