Sample size:
All cases available in medical campus university of Khartoum in the
period of data collection.
Equation used:
\begin{equation}
no=\frac{Z^{2}\text{pq}}{e^{2}}\nonumber \\
\end{equation}Where: no=initial sample size required,
z = probability that e is not exceeded.(e score of 1.645 corresponds to
90%confidence level),
p= expected prevalence (estimated as 0.5),
q=1-p,
e=maximum acceptable random sampling error (here is 5%)
So my initial sample size (no) is= 0.67650625/(5%)= 270
So by this equation: the last sample size n= no/(1+(no/N)), where N is
population size which is 3814 medical campus students, it was found to
be 253 samples from the study population.