# 2011 Stats Free Response Question

#### SuckyComedian

##### New member
I don't understand B for this problem. I already did A...

During a flu vaccine shortage in the United States, it was believed that 44 percent of vaccine-eligible people received flu vaccine. The results of a survey given to a random sample of 2,350 vaccine-eligible people indicated that 978 out of the 2,350 people had received flu vaccine.

a) Construct a 99 percent confidence interval for the proportion of vaccine-eligible people who had received flue vaccine. Use your confidence interval to comment on the belief that 45 percent of the vaccine-eligible people had received flu vaccine.

b) suppose a similar survey will be given to vaccine-eligible people in Canada by Canadian health officials. A 99 percent confidence interval for the proportion of people who will have received flu vaccine is to be constructed. What is the smallest sample size that can be used to guarantee that the margin of error will be less than or equal to 0.02?

#### tkhunny

##### Moderator
Staff member
I'm not planning to clik the external link, but off the top of my head...we don't now the variance, so we're using the value that will maximize the estimate.

I demonstrate.

0.1 * 0.9 = 0.09
0.2 * 0.8 = 0.16
0.3 * 0.7 = 0.21
0.4 * 0.6 = 0.24
0.5 * 0.5 = 0.25

Get the picture?

#### SuckyComedian

##### New member
I'm not planning to clik the external link, but off the top of my head...we don't now the variance, so we're using the value that will maximize the estimate.

I demonstrate.

0.1 * 0.9 = 0.09
0.2 * 0.8 = 0.16
0.3 * 0.7 = 0.21
0.4 * 0.6 = 0.24
0.5 * 0.5 = 0.25

Get the picture?
Oh right! I remember this now Thanks! and the link is just to a screen shot. It let's you crop the screenshot really quick and the uploads it to their site for you automatically. Nothing bad xD