00:02
76 percent watched the winter olympics.
00:05
So in a survey of 100 americans, 76 percent watched the winter olympics.
00:15
With 80 percent confidence, the bridgestone survey team claims there's a margin of error of 5 .5 percent.
00:32
Was the survey team accurate in reporting a 5 .5 percent margin of error? so let's calculate it out.
00:44
The critical value for 80 percent confidence is 1 .28.
00:56
So the margin of error should be 1 .28 multiplied times the square root of 0 .76 times 0 .24 over 100.
01:12
And that is 0 .05466, which would be 0 .055 approximately.
01:22
I guess we could put that instead of here.
01:24
Let's put that here.
01:25
So yeah, that's accurate.
01:27
For the second part of the question, what sample size is needed for a margin of error of 5 percent with 90 percent confidence? so we'll do 1 .645...