View Full Version : Hypothesis test help plz

04-11-2010, 12:31 PM
I am getting a different answer than the prof. provided on the answer key for the following prob and have been trying since yesterday to make this work and need help!:

A report from the National Bank of Information claimed that 29.5% of US State Legislators are women. But the League of Women Voters believes that the real proportion is higher. They took a sample of 180 US Legislators, where 68 were women. Do these data support the Leagues opinion on the issue? Use "alpha" = 5 %.

Step 1-H knot P=0.295 and H-a is P is > .295

Step 2-"alpha" = 5%

Step 3- (p-hat-Po)/sq root of Po (1-Po)/n

Step 4-if z is > 1.65 then reject H knot

Step 5-with n=180 and p-hat = .35
this is where I put all the variables into formula of step 3 and my answer was 1.62 whereas the prof got 2.44, prof did not put the formula on the answer key so I don't know if that is the correct formula

any help would be appreciated!

04-11-2010, 12:53 PM
The answer of 2.44 is correct! You must make some mistake in your calculation.

Population proportion -p is 0.295
Sample proportion -hat p is 68/180 = 0.37778

Step 1 is OK
Step 2 is OK alpha of 5% bring z=1.645
Step 3 is the following: (0,37778-0,295)/(sqr((0.295*(1-0.295))/180)) = 2.4353
Step 4: 2.4353 > 1.645 =) reject the null hypothesis

The formula of the step 3 is:
z-score= (hat p - p / ((sqrt(p(1-p) / n))

Best regards

04-11-2010, 01:35 PM
Thank you so much! This helps me keep what little sanity I have left from this course :)