Can someone help me with this maths question on stratified sampling?

John wants to do a survey of the competitors. He uses a stratified sample of exactly 50 comeptitors according to each age group.


16-18 years- 120


19-24 years- 250


25+- 200





work out the number of competitors in each age group that should be in his stratified sample

Can someone help me with this maths question on stratified sampling?
Stratified Sampling means having the right proportions of people in your survey.





The total number of people he could ask is 120 + 250 + 200 = 570.





You want 50 people, out of this 570.





To work out how many 16-18s:


(50/570) x 120 =


10.5 ----%26gt; Round to 11





For 19-24s:


(50/570) x 250 =


21.9 ----%26gt; Round to 22





For 25+:


(50/570) x 200 = 17.5 ---%26gt; Round to 18





11 + 22 + 18 = 51. So one of them you need to round DOWN instead of up, even though all of them would round up.





The decimals after 10.5 were lower than those after 17.5, so round that one down to 10.





10 + 22 + 18 = 50





Hope that helps