Sample Size Determination and Sampling Procedures

Sample size calculations for the survival status and predictors of mortality among stroke patients at FHCSH, for objectives one and two, were determined and the largest one was taken as the sample size for this research. That is, the sample size for the first objective was calculated using the following data and assumptions: 95% confidence interval, 80% power, and hazard ratio (4.93) (Fekadu et al, 2019) the formula having two stepsâ

Where

- M is number of expected events (death)

- is the significance level two sides (5% the value is 1.96)

- have the value of 80% power (0.84)

- is logarithm of the hazard ratio (4.93) (Fekadu et al, 2019).

- is the fraction of subjects allocated to the first group (by general cohort study expected ratio of 1 to 1 exposed-non exposed ratio)

where n is the number of subjects to be followed,

M-is the number of events (66) and P is the overall probability of an event (death) at the end of the study (21.6%) (Fekadu et al, 2019) [31].

The sample size calculation for objective two is obtained from different literature and is calculated by Stata version 13 by considering the following assumptions: confidence level 95%, power 80% and exposed to unexposed ratio of 1:1 by general cohort study, standard deviation and correlation of covariates 0.5 and 0, respectively. Finally, by adding 20% of the lost follow-up, the final sample size was 368. Therefore, the sample size for this research was 368, which is the largest among the sample sizes calculated for both the first and the second objectives.

In Felege Hiwot Comprehensive Specialized Hospital, there is a list of stroke patients in the electronic database. Those over the age of fifteen were chosen first from those under the age of fifteen based on their electronic registrations. Five-year registered stroke patients confirmed by imaging using CT/MRI were included in this study. Then, study participants were selected by a simple random sampling technique with a lottery method.