Question

Ruby made a one-sample z interval for a proportion and used the critical value z*=1.476.

Answer 1

Answer:

Step-by-step explanation:

 

When calculating the standard error, is it better to calculate the unbiased standard deviation of the sample and divide that by the positive root of the sample size,

here sqrt( (30*(0.4)^2 + 20*(0.6)^2) / 49 / 50) = 0.0699854...,

or use the formula of the standard error of the sample distribution, using p hat as an estimate of p ?

here sqrt(0.4 * 0.6 / 50) = 0.0692820...

The two don't give the same result. Sal uses both methods in different videos without saying why, so some extra explanation would be helpful!