# Sample Size Calculations with JMP

#### NN_STAT

##### New Member
Hello,

I have used the sample size calculator of JMP for a single proportion. I need to add to my report the formula "I used" (JMP did). I couldn't find it in the JMP manual. Does anyone know how the JMP calculates a sample size for a single proportion, given the real known proportion, the hypothesized proportion, the significance level and the power ?

thank you

#### BGM

##### TS Contributor
You can derive it.

If you know the hypothesized proportion and the significance level, you know the rejection region in terms of the sample size $$n$$

Under this rejection rule, if you know the power and the real known proportion, you can solve the $$n$$ out.

#### NN_STAT

##### New Member
thanks for the hint, but I am afraid I have no clue how to do this...was looking for a link for the equation, but nothing came up.

what confuses me is how the power comes in. I know how to derive n from a CI formula for example, but not like this...

#### NN_STAT

##### New Member
I found a formula, the delta doesn't fit, it belongs to CI...if I remove it I get similar results to JMP, or is it just a coincidence...

I have no idea how to derive it like you suggested.

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#### BGM

##### TS Contributor
Ok do you know how to do the proportion test with normal approximation? with significance level $$\alpha$$, hypothesized proportion $$p_0$$ and sample size $$n$$