ALPHA BETA POWER (ch 9) Flashcards
Pregnancy test. What is NULL and ALTERNATIVE?
Ho: NOT PREGNANT Ha: PREGNANT
example of TYPE I with a pregnancy test:
test says “pregnant” but subject is not pregnant
example of type 2 error with pregnancy test:
test says “not pregnant” but subject is pregnant
example of power with a pregnancy test
the percent of pregnant women that get a “pregnant” test result. The probability of it correctly detecting what it was designed for.
A school system is testing the effectiveness of after school MCAS math program. What is the NULL and ALTERNATIVE?
Ho: program doesn’t work Ha: program works
example of type 1 error for a school system trying a new after school math MCAS program (and implications)
You think the program worked when it actually didn’t. District spends money on a useless program.
example of type 2 error for a school system trying a new after school math MCAS program (and implications)
You don’t think it works when it actually does. You miss an opportunity to adopt a program.
example of POWER for a school system trying a new after school math MCAS program
The likelihood you detect that a good program works.
A school system is testing the effectiveness of after school MCAS math program. If the program works, what is the only type of error you could make?
Type 2. You didn’t notice the effect. You failed to reject.
A school system is testing the effectiveness of after school MCAS math program. If the program does not work, what is the only type of error you could make?
Type 1. You thought it worked but it didn’t. You rejected when you shouldn’t have.
A school system is testing the effectiveness of after school MCAS math program. If you conclude that the program works, what is the only type of error you could make?
Type 1. You thought it worked but it didn’t. You rejected when you shouldn’t have.
A school system is testing the effectiveness of after school MCAS math program. If you conclude that the program doesn’t work, what is the only type of error you could make?
Type 2. You didn’t notice the effect. You didn’t think that it worked, but it did. You failed to reject.
What is Type 1 error?
We reject when we shouldn’t have (the null was actually true)
What is probability of type 1 error?
alpha
What is probability of type 2 error?
Beta
What is power?
The probability that you correctly rejected a false null
What is Type 2 error?
We fail to reject when we should have rejected (the null was actually false)
If you reject, what is the only type of error you could make?
Type 1 (Nystrom is a Type 1 reject)
Can you decrease alpha while increasing power (even though they move together?)..
Yes.. INCREASE SAMPLE SIZE. If you increase the sample size, you can decrease alpha and increase the power.
If the null is false, what is the only error you could make?
Type 2
If the null is true, what is the only error you could make?
Type 1
How are power and alpha related?
they go up and down together
How else can you explain power?
Power to correctly detect what you were trying to detect
How can you increase power?
Increase alpha or increase sample size..
Can you draw the alpha/beta/power diagram?
Think of the pregnancy worksheet.
How can you decrease alpha and beta at the same time?
increase sample size. this will also increase power.
What is beta?
It is probability that you’ll make a Type II error.. P(Type II error)
How can you think of TYPE 2 error?
the missed opportunity error.. You failed to see an effect
how are beta and power related
as one increases, the other decreases, and vice versa. They have to because they BOTH ADD TO ONE!!! Power + Beta = 1
What is alpha?
It is the rejection threshold. You reject p-values below it.. It is how willing you are to make a Type 1 error? alpa=P(Type I error)
What is effect size?
Difference between null and true parameter. something we don’t know
how are alpha and beta related?
as one increases, the other decreases, and vice versa
If you fail to reject, what is the only type of error you could make?
Type 2
