How do i work out stratified samples for year 7's and 10's?

Question

Theres 30 pupils altogether and theres 224 year 10s and 191 year 7s.

Answer 1

Welcome to Mayfield coursework eh !!!

Find combined total of pupils ( 415 )
Divide this by 30 ( the sample size )
Finally multipy this answer by the totals for each individual year group ( year 10 = 16.19.... year 11 = 13.81.... )
This gives us 16 for year 10 and 14 for year 11 when rounded to whole numbers.
Now choose the pupils randomly and so the coursework begins.

Answer 2

H: The number of strata in the population.
N: The number of observations in the population.
Nh: The number of observations in stratum h of the population.
Ph: The true proportion in stratum h of the population.
σ2: The known variance of the population.
σ: The known standard deviation of the population.
x: The sample estimate of the population mean.
xh: The mean of observations from stratum h of the sample.
ph: The proportion of successes in stratum h of the sample.
sh: The sample estimate of the population standard deviation in stratum h.
s2h: The sample estimate of the population variance in stratum h.
n: The number of observations in the sample.
SE: The standard error of the estimate. (This is the standard deviation of the sampling distribution of the sample estimate.)
Σ: Summation symbol. ( To illustrate the use of the symbol, Σ xh = x1 + x2 + ... + xH-1 + xH )