# Stratified Sampling

Stratified sampling question and how to work it out! :)

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## Stratified Sampling

Q) Albert owns a farm, he wants to check the overall health of his animals he chooses cows, horses and rabbits.

He decides to take a sample size of 30.

Animal: Cows   Horses   Rabbits
Total:     40         60           50
Sample:   8           12         10

A) how I worked it out:

40+60+50= 150

150/30= 5

40/5=8      60/5=12      50/5=10   Thats how many animals he checks

To check you've done it correctly just add 8+12+10=30 it equals 30 which is your sample size.

Hope that helped you :):)

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## Harder Sampling

I was doing a past paper the other day and it had a stratified sampling question in but not like the one on the other card i did, so i thought i'd tell you how to complete it incase you come across one like it and don't know how to work it out.

Q) A sample of runner was taken from a group, stratified by age to complete a survey. Complete the table;

Age group   Frequency   Number in sample
18< r<30           240              12             <------------(first one done for you)
30<r<40           450                23
40<r<50            170               9
50<r<70           80                   4

What i did;   240/12=20 (20 is the sample number we need to make it into a fraction- 1/20)
then you do (450/20)x1 = 23 and so on... (170/20)x1=9...

I didn't get how to do this question at first, but i worked it out after so i hope it helped you :)

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Hi Purple Jaguar

bmt

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hello

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Hiya :)

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Thanks, I've only just learnt how to do this so it really helped me understand it more. ;)

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