
What is prevelance and how is it calculated?
P = (number of exisiting cases of disease at a given point in time)/(total population)
P = incidence x duration

What is incidence?
Number of new cases that occur during a period of time.

What is cumulative incidence?
Proportion of people whop became diseased during a perior of time (probability/risk of disease during the period of time).

What is sensitivity and how do you calculate it?
 Proportion of those with disease who tested positive
 Sensitivity = TP/(TP + FN)

What is specificity and how do you calculate it?
 Proption of people without disease who test negative
 Specificity = TN/ (TN + FP)

What is the PPV and how do you calculate it?
 Proportion of people who test positive that are really diseased
 PPV = TP / (FP / TP)

What is the NPV and how do you calculate it?
 Proportion who test negative and really aren't diseased
 NPV = TN / (TN + FN)

What factors change the PPV & NPV?
changing disease incidence /prevalence

What's a type 1 (alpha) error? What is it's measurement?
Stating that there is an effect or difference when none exists; p is probablility of making type 1 error

What's a type 2 (beta) error?
Stating that there is not an effect or difference when one exists;

What is the power of a study?
Probablilty of getting the right answer to the study.

What factors change the power of a study?
 Number of points in the population
 Differnece in complaince between groups
 Size of expected effect

What's a confidence interval?
Range of values in which a specified probability of the means are expected to fall.

When is a confidence interval useless?
 Interval includes 0 or 1 = H_{0} is true
 Intervals overlap = not significantly different

What is an experimental study with random allocation?
Randomised controlled trial

What's an experimental study without random allocation?
Nonrandomized controlled trial

what's an ovservational study with no comparison group?
Descriptive study

What's an ovservational study with a comparison group?
Analytical Study (cohort, case control, cross sectional)

What's a cohort study?
 Analytical Study
 Taking an exposure group and looking forward for an outcome

What's a Casecontrol study?
Analytica study looking from an outcome back to evaluate for exposure

what's a crosssectional study?
Looking at the exposure and outcome status at the same moment in time

What's the correlation coeficient and what does it mean?
 (r) bewtween 1 and +1
 The closer to +1 the stronger the correlation between the two variables

What is the coefficent of determination?
 r^{2}
 this is the value that's reported

What is a case report and what are it's purposes?
 Describe experience of individula/population
 First step in identification of new things
 1. describe and evaluate trends in outcomes
 2. provide data for panning
 3. suggest new research

What's a correlation/ecological study and what are strengths/limitations?
 Study of group characteristics; measure of association; noncomparative to another group
 Strengths: quick, cheap, easy
 Weaknesses: inability to link exposure and disease; lack of control over confounding factors

What is ecologic fallacy?
Inapporpriate inference from ecological data (relationship of groups doesn't mean relationship of individuals)

What are the pro/cons of cross sectional study?
 Strengths: quick, cheap, establish "burden of diease"
 Weaknesses: confuses causation and correlation

What are the pro/con of case control studies?
 Strengths: evaluation of rare diseases with long latency, quick and cheap, multiple factors for a single disease
 Weakness: limited for rare exposures, no incidence rates, difficult to establish temporal relationship, prone to bias

What are the strengths of a cohort study?
 Rare exposures, good information collected
 Least bias, clear temporal relationship
 direct measurement of incidnce in exposed vs nonexposed

What are limitations of cohort studies?
 Ineficient for rare diseases
 Expensive and time consuming
 Retrospectives are more vulnerable to bias

What is an experimental study? What are key components of the study?
 controlled expeirment
 Randomization, blinidng, placebo controlled
 Cross over  each subject serves as their own control
 Factorial design  allows for evaluation of multiple hypothesises

What's primary disease prevention?
Remove the risk (ie vaccination)

What's secondary disease prevention?
Early detection and treatment (ie, pap smear)

What's tertiary disease prevention?
reduce complications of the disease (ie; insulin for diabetes)

How do you fill in the box for all the calculations?

What's an odds ratio and how is it calculated?
 odds of being diseased if exposed: odds of being diseased if unexposed
 (A/B) / (C/D) = OR

Whats an absolute (attributable) risk and how's it calculated?
 % increase of disease attrributabe to exposure

What's an absolut (attribuateble) risk reduction and how's it calculated?
 % differnce in diseased between normal and treated groups

What's the relative risk and how's it calculated?
 The probability of getting diseased in exposeure group when compared to normal

What's the Relative risk reduction and how's it calculated?
 % attributable of diseased to a factor (ie: 1/3 of pneumonia is caused by smoking)

How do you calculate Confidence Interval
 Confidence Interval = (mean ±Z( σ /√N))
 Z = 2; σ = SD

