00:01
So we're going to find the largest sample size that's needed, the n max, for a proportion example.
00:07
And so we have that in part a, that n is 2 ,500.
00:13
The p hat is 0 .5, and 1 .96 times the standard error of the p hats is equal to 0 .05, which again means this is the margin of air.
00:25
Or that the standard error here is equal to .05 divided by 1 .96.
00:33
And the formula that we will need to use is for n max is that .25 times capital n, and then the capital n minus 1, and then the standard air squared, n plus .25.
00:52
So we will have .25 times our 2 ,500, and then we'll have 2499 times the standard error, so we'll have that .05 divided by 1 .96.
01:08
I'm not going to bother writing down what that is.
01:10
They do show that in the example, but, you know, i don't need it, so we just need to know how to find it.
01:17
And so i'll carefully put this in.
01:20
I have left parentheses, 0 .25 times 2 ,500.
01:23
That's at my numerator divided by left parentheses and then 2499 times in parentheses that 0 .05 divided by 1 .96, that quantity squared plus 0 .25.
01:38
And then i can close that parenthesis off.
01:40
And we find that that maximum size that we would need is 33 .1...