Research Flashcards
(40 cards)
type I error
false +
you see a difference but there really isn’t one
overcalling it
type II error
didn’t get a difference but there should have been one
p value affects
*establish likelihood of type I error
*smaller p value=more likely a true accurate difference
under calling it
CI
narrow = less variable data
correlation coefficient
0-1
1=better correlation
sensitivity
measure of true +
false negative = 1-SN
use a negative test to rule out
associated with -LR
specificity
measure of true negative
use a + SP to rule in
false + = 1-SP
PPV- positive predictive value
patients who test positive who actually have the disease
NPV- negative predictive value
patients who test negative who actually don’t have disease
incidence
rate of new cases in specific time
RATE OF CHANGE to express risk of disease
prevalence
of cases at a specific time
CANT predict probability because it’s not a rate of change
likelihood ratios
closer to 1 = less useful
+LR = Sn / (1-Sp)
-LR = (1-Sn) / Sp
odds ratio
odds of event in control group / odds in experimental
P vs alpha value- stat significance
P value must be lower than alpha to be statistically significant
level I evidence
high quality from RCT, diagnostic studies, prospective studies
level II evidence
lesser quality diagnostic studies, prospective studies, RCT
such as improper randomization, <80% f/u, no blinding
level III evidence
case control study or retrospective
level IV evidence
case series
level V evidence
expert opinion
specificity
ability to be negative when a variable is absent
measures the proportion of negatives which are correctly identified.
sensitivity
ability to be + when variable is present
very sn = good screening tool
proportion of those with a positive test given that they have the condition being tested for
LR values
+ LR
>10 = large probability of condition
5-10 = moderate
<5 = small
1 = no change
- LR
<0.1 = large probability
0.1-0.2 = moderate
>0.2 = small
1 = no change
likelihood ratio definition
The likelihood that a test result would be expected in a patient with the target disorder compared with the likelihood of the results with a patient without the disorder
Tells you how much a test result changes the pre-test probability of being correct
+ LR = how much to increase suspicion of condition based on + test
-LR = how much to dec suspicion of condition based on in test
how to control type II error
statistical power
increase number of subjects to decrease error
how to control type I error
alpha - significance value