Answer:
a = 14
b = 15
c = 15
d = 18
e = 18
Step-by-step explanation:
The stratified sampling works as follows:
stratified sampling = (Population of subgroups)*(total sample size)/(entire population)
in this case, sample size = 80
entire population = 140 + 150 + 150 + 180 + 180 = 800
Population sample is the number of students of each year (for year 7, the population of subgroup is 140, and so on)
whith this equation we can find all the missing values:
a = (140)*(80/800) = 14
b = (150)*(80/800) = 15
c = (150)*(80/800) = 15
d = (180)*(80/800) = 18
e = (180)*(80/800) = 18
