I need some help with this problem, I've been struggling with it for a long time but i just cant seem to get it!
This is it:
About 22% of the residents of California were born outside the United States. You choose an SRS of 1,000 California residents for a sample survey on immigration issues. You want to find the probability that 250 or more of the people in your sample were born outside the United States. What is the probability that 250 or more of the people in your sample were born outside the United States?
This is it:
About 22% of the residents of California were born outside the United States. You choose an SRS of 1,000 California residents for a sample survey on immigration issues. You want to find the probability that 250 or more of the people in your sample were born outside the United States. What is the probability that 250 or more of the people in your sample were born outside the United States?
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Tasyra
The population mean = 1000 x 22% = 220
The population std dev = sqrt (1000 x 0.22 x 0.78) = 13.1
P(X > 250) = P[z > (250 - 220) / (13.1) ]
= P(z > 2.29) = 0.0110 [from Standard Normal table]
hope that helps
The population mean = 1000 x 22% = 220
The population std dev = sqrt (1000 x 0.22 x 0.78) = 13.1
P(X > 250) = P[z > (250 - 220) / (13.1) ]
= P(z > 2.29) = 0.0110 [from Standard Normal table]
hope that helps
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The claim is that 22% of California residents is foreign born. Call it p, and p=22% or p=0.22 so p+q=1, therefore q=1-p or q=0.78
You want to test that claim using a sample of 1000 people, that's your sample size n=1000, you are asked to find out that the probability of 250 of those people are foreign born that your X bar=250, so your can find your proportion, call it p hat( p with sign of a hat on top....notation ) p hat=250/1000, p hat=0.25. Now find the test statistics Z=(p hat- p)/ square roots(p*q)/n
By plugging the number Z=2.29 the area corresponding in the table is 0.9890 so your P value is 1-0.9890 or 0.11 thus your probability 0.011 or 1.1%
It is a right tail test.
You want to test that claim using a sample of 1000 people, that's your sample size n=1000, you are asked to find out that the probability of 250 of those people are foreign born that your X bar=250, so your can find your proportion, call it p hat( p with sign of a hat on top....notation ) p hat=250/1000, p hat=0.25. Now find the test statistics Z=(p hat- p)/ square roots(p*q)/n
By plugging the number Z=2.29 the area corresponding in the table is 0.9890 so your P value is 1-0.9890 or 0.11 thus your probability 0.011 or 1.1%
It is a right tail test.
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I draw a line 3 feet long. How long is the line?
Well, obviously, 3 feet, right?
Wrong!! it is 36 inches. It is also 1 yard. It is also 1 / 1760 of a mile.
The point is that given some measure, there are usually MANY ways to describe that measure.
Now, take a distribution of some sort. There are also many ways to describe that distribution. We can "talk" about how many units are above a certain point, what percentage is above a certain point, or a "distance" along the horizontal axis (absissa).
Well, obviously, 3 feet, right?
Wrong!! it is 36 inches. It is also 1 yard. It is also 1 / 1760 of a mile.
The point is that given some measure, there are usually MANY ways to describe that measure.
Now, take a distribution of some sort. There are also many ways to describe that distribution. We can "talk" about how many units are above a certain point, what percentage is above a certain point, or a "distance" along the horizontal axis (absissa).
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