Source Population, Study Population, and Sample Size

The source population of this study was individuals with fractures who were visiting the orthopedics department. The study population was all individuals with lower limb fractures who were visiting the University of Gondar referral hospital (orthopedic OPD) during the study period. A sample size was calculated using a single population proportion formula based on the assumptions; 95% confidence interval (CI), 50% prevalence, 5% precision, 15% non-response, and contingencies. Since there was no previous study done in similar area and setting. The sample size of this study was calculated as:

n = (za/2)² p (1-p)/d²

n= (1.96)²* (0.5)* (0.5)/(0.05)² = 384.16~385

However the total number of lower limb fracture patients receiving orthopedics treatment annually was below 10,000. So the samples were taken from a relatively small population (N=400), the required sample size was obtained by using the following calculation. Since on average 100 lower limb fracture patients are seen in orthopedics OPD. By considering this, a total of 400 lower limb fracture patients have visited the hospital during the data collection period.

nf =n/1+n/N

n=385/1+385/400=385/1.96=196.4

n=196.4 for the precision considering 15% expected contingency the final sample size is 226. Finally 226 study participant were enrolled with simple random sampling method.