Statistical Power Flashcards
1
Q
describe when false positive are common
A
false positives are common when:
- the p-value for significance is high
- solution: lower the p-value (.01 instead of .05)
- the condition is rare
- solution: reserve testing for high-rsk cases, thus increasing the base rate in the tested population; this is screening
- both of these increase the rate of false-negatives
2
Q
describe minimizing the harm from false positives
A
- screening tests have high false positives rates but are easy to implement, which include:
- mammogram for breast cancer
- fecal occult blood test for colon cancer
- a positive test will be followed by a more invasive test that has a lower rate of false positives, which include
- biopsy or other surgery
- colonoscopy
- this 2-layer screen minimizes both false positives and false negatives
3
Q
power is higher if between-group differences are ___, within-group variation is ___ and/or samples are ____
A
power is higher if between-group differences are large, within-group variation is low and/or samples are large
4
Q
describe statistical power
A
if there is an effect, what are the chances this test will (correctly) reject the null hypothesis?
5
Q
list the 3 ways you can increase power
A
- larger between-group differences
- less within-group variation
- larger samples
6
Q
describe how to maximize between-group differences
A
- compare the best examples of one group to the best examples of the other
- for example: compare only those family members who are related by blood, rather than those who married in
7
Q
describe methods to minimize within-group variability
A
- recruit subjects who are as similar as possible except for the outcome of interest
- for example:
- compare the bride’s female relatives to the groom’s female relatives (eliminates variability due to gender)
- compare only the adults of each family (minimizes variability due to age)
