Formulas Flashcards
What is the attack rate and what is the secondary attack rate?
Primary attack rate - Infected people / people
Secondary attack rate - Infected people besides the source / people besides the source
How do you calculate the odds ratio?
Odds of exposure in cases / Odds of exposure in controls
(AD/BC)
What does relative risk mean and how is it calculated?
compares the two attack rates (Exposed AR / Unexposed AR) so
(A/(A+B)) / ((C/(C+D)
What level of relative risk means what?
If Risk > 1: Positive association between exposure and illness, or increased risk
If Risk = 1: No data association
If Risk < 1: Risk for unexposed
How do you set up a contingency table? What does A, B, C, and D represent?
—————sick | not sick
_________________________________
Group 1 | A | B
Group 2 | C | D
How do you calculate point prevalance?
People infected in certain period / population
How do you calculate incidence rate?
New cases / (Timeframe x total population)
What is an incubation period?
Incubation period: How long it takes to develop symptoms to the date exposed
What is the chi-square algorithm?
(T(ad-bc)2)/(H1H0V1*V0)
After calculating the chi-square, at what number is the association statistically significant?
3.841
How do you calculate the measure of association?
(A / (A + B)) / (C / (C + D))
How do you calculate the odds ratio?
AD / BC
