00:01
A study was conducted to determine the proportion of people who dream in black and white instead of color.
00:06
So we have people who are over the age of 55 and we have people who are under the age of 25.
00:16
So among 317 people over the age of 55, 79 dream in black and white.
00:22
And among 310 people under the age of 25, 10 dream in black and white.
00:29
We're going to use a significance level of .01 to test the claim.
00:33
That the proportion of people over 55 who dream in black and white is greater than the proportion for those under 25.
00:40
So let's let the 55 be group 1 and the under 25 be group 2.
00:47
So our null hypothesis would be that p sub 1 minus p sub 2, well let's just say p sub 1 is equal to p sub 2 so that's how they are writing this.
00:57
Versus the alternative that p sub 1 is greater than p sub 2.
01:02
So our point estimate for group 1 is .249 and our point estimate for group 2 is .032.
01:17
And before we calculate our test statistic let's find our pooled proportion.
01:23
Sometimes we call it p sub c.
01:25
So we're going to take 317 divided by 627 times .249 plus 310 divided by 627 times .032 and that is going to give us .142.
01:44
So our z -test statistic is .249 minus .032 divided by the square root of .142 times 1 minus .142 over 317 plus .142 times 1 minus .142 over 310 and that is going to give us a test statistic of 7 .78 with a corresponding p -value of essentially 0.
02:15
So the p -value is less than our significance level which means we are going to reject our null hypothesis...