Code:

```
df <- data.frame(ID = c(1,2,3,4,5,6,7,8,9),
School = c("A","A","A","B","B","B","C","C","C"),
Test_Method_A = c("1A","2A","3A","1A","2A","3A","1A","2A","3A"),
SchoolSystemA_Score = c(80,75,25,87,65,15,66,90,65),
Test_Method_B = c("1B","2B","3B","1B","2B","3B","1B","2B","3B"),
SchoolSystemB_Score = c(78,56,80,58,65,98,79,55,70))
df
ID School Test_Method_A SchoolSystemA_Score Test_Method_B SchoolSystemB_Score
1 1 A 1A 80 1B 78
2 2 A 2A 75 2B 56
3 3 A 3A 25 3B 80
4 4 B 1A 87 1B 58
5 5 B 2A 65 2B 65
6 6 B 3A 15 3B 98
7 7 C 1A 66 1B 79
8 8 C 2A 90 2B 55
9 9 C 3A 65 3B 70
```

But to make a proposal I need to give an indication for the sample size, and I am very unsure about how to calculate this. So what I think I should at least know is the variance of the SchoolSystemA_Score and SchoolSystemB_Score, and the effect size I would at least want to know is 5%.

I'm just not really sure how I should split the groups (or shouldn't)

and what way to do this, is

Code:

`pwr.t.test(d=d, sig.level=.05, power = .90, type = 'two.sample')`

Sorry this might be very obvious for many, but I've tried to find articles/literature on this but I get very stuck. mostly because I can;t seem to translate it to my dataset.. Could anyone help me with this, very much appreciated!