I know how the formula works. But I'm conducting a research study (thesis) and am confused as how to use it during sampling different populations.
For example, I am going to survey three different schools with the year level and gender as a variable. These are not the real data of my research, just random number examples.
SCHOOL 1 POPULATION
Freshmen - 98
Sophomore 100
Junior - 200
Senior -34
SCHOOL 2 POPULATION
Freshmen - 35
Sophomore 87
Junior - 100
Senior -341
SCHOOL 3 POPULATION
Freshmen - 124
Sophomore - 200
Junior - 166
Senior - 78
I'm pretty sure you don't just use the formula right away. I remember we used percentages and stuff, but I forgot how the exact steps worked. After which, you're supposed to get a number you can use in identifying which students to sample. (stratified sampling. e.g. you get 9 and therefore every 9th student will be interviewed)
Please help, I don't want to screw up during defense panel because of my sampling.