Public Health Formulas Flashcards

1
Q

Sensitivity

A

1 - FN rate

Ruling out disease (screening)

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2
Q

False Negative Rate

A

FN / FN + TP

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3
Q

Specificity

A

1 - FP rate

Ruling in disease

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4
Q

Incidence

A
# new cases / # of people at risk         
(per unit of time)   

EXCLUDE PATIENTS THAT ARE ALREADY DIAGNOSED

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5
Q

Negative likelihood ratio

A

(1 - sensitivity) / specificity

(FNrate) / (TNrate)

probability of negative result in patient with disorder / probability of negative result in patient without disorder

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6
Q

Positive likelihood ratio

A

Sensitivity / (1 - specificity)

(TP rate) / (FP rate)

probability of positive result in patient with disorder / probability of positive result in patient without disorder

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7
Q

Prevalence

A

of existing cases / total # of people in a population

(at a point in time)

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8
Q

Prevalence / 1 - prevalence

steady state population

A

incidence rate X average duration of disease

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9
Q

Relative Risk

A

[a/(a+b)] / [c/c+d)]

incidenceof disease in exposed group / incidenceof disease in unexposedgroup)

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10
Q

Relative Risk Reduction

A

1 - RR

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11
Q

Odds Ratio

A

(a/c) / (b/d)

a x d) / (b x c

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12
Q

Exposure Attributable Risk

A

(incidence ratein exposedgroup) -(incidence ratein unexposedgroup)

a / (a + b) - c / (c + d)

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13
Q

Population Attributable Risk

A

(incidence ratein the entire studypopulation) -(incidence ratein the unexposedgroup)

(a + c) / (a + b + c + d) - c / (c + d)

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14
Q

Attributable Risk %

A

[(RR-1) / RR] X 100

(Attributable Risk / Incidence of disease in the exposed group) X 100

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15
Q

Attributable Risk Reduction (ARR)

A

(absoluteriskin the unexposedgroup) -(absolute riskin the exposedgroup)

c/(c + d) – a/(a + b)

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16
Q

Number Needed to Treat (NNT)

17
Q

Number Needed to Screen (NNS)

18
Q

Number Needed to Harm (NNH)

19
Q

Hazard Ratio

A

Incidenceof outcome in exposed group / incidenceof outcome in unexposedgroup

[a / (a + b)] / [c / (c + d)]

20
Q

Absolute Risk Reduction is also known as _______.

A

Risk difference

21
Q

Case fatality rate is also known as _______.

22
Q

Case Fatality Rate

A

(# deaths from a specific condition / # cases with the same specific condition) X 100

23
Q

Attack rate is also known as _______.

A

Cumulative incidence

24
Q

Attack Rate

A

People who become ill / Total people exposed

DO NOT SUBTRACT DEATHS FROM DENOMINATOR

25
Mortality rate is also known as _______.
Crude death rate
26
Mortality Rate (crude death rate) 
of deaths / total population size
27
Cause Specific Mortality Rate 
of deaths of particular disease / total population size
28
Standardized Mortality Ratio
Observed # of deaths / Expected  # of deaths
29
Maternal Mortality Rate 
(# of maternal deaths / # of live births) X 100,000
30
Perinatal Mortality Rate
[(# of stillbirths + # of infant deaths during first week after birth) / total number of births] X 1,000
31
Crude Birth Rate
of live births / total population size
32
Fetal Mortality Rate
[(# of infant deaths during the first 24hours after birth) / (total number of live births)] X 1,000
33
Reliability Coefficient
Variance of the true value (population variance) / Variance of the measured value (sample variance) Reliability coefficient = 1 → the variance of the sample mean is equal to the variance of the true measure → the study/test is highly reliable
34
Standard Deviation (σ)
√variance
35
Variance
SDˆ2
36
Standard Error of the Mean
Standard deviation / √(sample size)
37
Standard normal value (Z-score, Z-value, standard normalized score)
(value - population mean) / standard deviation Z-score for a 90% confidence interval = 1.64 Z-score for a 95% confidence interval = 1.96 Z-score for a 97.5% confidence interval = 2.24 Z-score for a 99% confidence interval = 2.58
38
Confidence Interval for Sample Mean
Mean +/-  Z (standard error of the mean) Mean +/- Z (standard deviation / √sample size) Confidence interval (CI) = 1 – α.
39
Coefficient of Determination
rˆ2 Amount of variance in one variable that can be explained by variance in another variable