5 thoughts on “Sample Size Determination (Q3) (Preview)”

Jh.lee26

Hi jason The formula of the sample size in the formula sheet has bracket only over the top party which is {[(z) (a/2)(SD)]^2} / B
It is supposed to be {[(z) (a/2) (sd)] / B} ^2 right?

Jh.lee26 was correct – The denominator SHOULD be within the brackets and the cheat sheet has been updated to reflect this amendment. The video shows the correct version of the formula.

There are two z-scores used in a confidence interval. The interval occurs between z=-2.575 and z=+2.575. Whichever one you use in the formula however will give you the same result since the value of z is squared (squared negative numbers are positive).

Hi jason The formula of the sample size in the formula sheet has bracket only over the top party which is {[(z) (a/2)(SD)]^2} / B

It is supposed to be {[(z) (a/2) (sd)] / B} ^2 right?

Correct?

Jh.lee26 was correct – The denominator SHOULD be within the brackets and the cheat sheet has been updated to reflect this amendment. The video shows the correct version of the formula.

When retrieving the z score, its a negative. so it was -2.575. Do we ignore that?

There are two z-scores used in a confidence interval. The interval occurs between z=-2.575 and z=+2.575. Whichever one you use in the formula however will give you the same result since the value of z is squared (squared negative numbers are positive).