Statistics Question (Calculator)

Question

Samples of size n produced sample proportions P^(hat) as shown. In each case decided whether or not the sample is large enough to assume that the sample proportion p(hat) is normally distributed.

a. n= 30, p(hat)= 0.72
b. n= 30, p(hat)= 0.84
c. n= 75, p(hat)= 0.84

I m not asking for answers to the problems. I just need to know how to calculate them on my TI-84 Plus Calculator.

I have tried STAT ---> TESTS ---> 5. 1- PROPZTEST

I filled in p as 0.72 and n as 30. Not sure what the x would be.

Am I even doing this correctly?

Answer 1

Hi Kimberly,

 

This question doesn't require you to use the stats menu on your TI. It's asking you to apply a rule of thumb that requires 2 things:

 

1. n ≥ 30

2. n × phat ≥ 5 and n × (1-phat) ≥ 5

 

Some but not all of a-c meet these conditions.

 

Note this is a rule of thumb so different texts or different instructors may have slight variations on this rule of thumb. Nevertheless, Part 1. gives us assurance that the sampling distribution of phat is centered around p and part 2. gives us assurance that the sampling distribution is symmetric. Together, they give us assurance that the bell curve is a good approximation for the distribution of phat.