Hello, my name is Hue Man, I am a senior nursing student at Tra Vinh University. Currently, I am doing my graduation thesis on: "Research on the rate of depression in the elderly using the GDS-5/15 scale and some related factors at the medical examination department". But the problem I am currently facing is the sample size calculation formula and how to process the data. Please can anyone give me advice or a solution. I sincerely thank you