Case Control Study
Cohort
Cross Sectional
Stages of Clinical Trial
1-small group of health volunteers
2 - small group of diseased
3 - large group of diseased
4 - post market surveilance
Sensitivity
TP/TP+FN
-Used to rule out a disease (picks up the most true positives)
Specificity
TN/TN+FP
-Used to rule in a disease (Picks out all the people who tested positive who actually have the disease)
PPV
TP/TP+FP
-The liklihood that given a positive test, the patient will actually have the disease
NPV
TN/TN+FN
-The liklihood that given a negative test result the patient will really not have the disease
Incidence
Prevalene
-The proportion of people who currently have the disease over the total population
Odds ratio
Relative Risk
Attributable Risk
(a/a+b)-(c/c+d)
Selection Bias
-Not selecting right patients, berkson is a part
Berkson’s Bias
-Some patients are lost to follow up and thus interfere with interpretation
Lead Time
-Earlier Diagnosis does not mean improved survival
Hawthorne
-Patients will change their behavior when they know they are being studied.
Standard Error of Mean
SD/(sqrt(n))
-Used to calculate confidence intervals
Positive Skew
Mean is greater than the median.
-The tail will be in the positive direction
Negative Skew
Mean is less than the median
-Tail will be in negative direction
Standard Deviation and SEM
- SEM is used to report confidence intervals and is standard deviation over the sqrt(n)
Type I Error
Type 2 error
T Test
-Used to compare two quantatitve variables