Public Health Sciences First Aid

Question 1

frequency of disease and frequency of risk-related factors are assessed in the present

what does this measure?

Answer 1

Cross-sectional study

disease prevalence

Question 2

compares a group of people with a disease to a group without disease

what does this measure?

Answer 2

case control study

odds ratio (OR)

Question 3

What are the four phases in clinical trials?

Answer 3

1. small number of healthy volunteers - is the drug SAFE
2. small number of pts with disease of interest - does it WORK
3. large number of pts randomly assigned either to the treatment under investigation or to the best available treatment (or placebo) - any IMPROVEMENT
4. postmarketing surveillance of pts after tx is approved - withdrawn from MARKET

Question 4

Sensitivity equation

Answer 4

= TP/ (TP+FN)

Question 5

Specificity equation

Answer 5

= TN/(TN+FP)

Question 6

PPV equation

Answer 6

= TP/(TP+FP)

Question 7

NPV equation

Answer 7

=TN/ (TN+FN)

Question 8

Prevalence equation

Answer 8

= (TP+FN)/(TP+FN+FP+TN)

Question 9

positive Likelihood ratio v negative Likelihood ratio

Answer 9

LR+ = sensitivity/ 1-specificity

LR- = 1-sensitivity/specificity

Question 10

In regards to likelihood ratios, what are indicators of a very useful diagnostic test?

Answer 10

LR+ >10 and LR- <0.1

Question 11

Odds ratio equation

Answer 11

= ad/cb

Question 12

relative risk is generally used in what kind of studies?

what is the equation?

what are interpretations of RR scores?

Answer 12

cohort studies

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

RR=1 then no association between exposure and disease

RR>1 then exposure associated with increased disease

RR<1 then exposure associated with decreased disease

Question 13

difference in risk between the exposed and unexposed groups

Answer 13

attributable risks

Question 14

the proportion of risk reduction attributable to the intervention as compared to a control

equation?

Answer 14

relative risk reduction

RRR = 1-RR

Question 15

the difference in risk attributable to the intervention as compared to a control

equation?

Answer 15

Absolute risk reduction

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

Question 16

When talking about number needed to treat, a lower number indicates…

equation?

When talking about number needed to harm, a high number indicates…

equation?

Answer 16

better treatment => NNT = 1/ARR

safer exposure => NNH = 1/AR

Question 17

study population selected from hospital is less healthy than general population

Answer 17

Berkson bias

Question 18

The Hawthorne Effect is an example of what kind of bias?

Answer 18

measurement bias

Question 19

What kind of bias is called Pygmalion effect?

Answer 19

observer-expectancy bias

Question 20

when a factor is related to both the exposure and the outcome, but not on the causal pathway - factor distorts or confuses effect of exposure on outcome

Answer 20

confounding bias

Question 21

early detection is confused with increased survival

Answer 21

lead-time bias

Question 23

Stating that there is an effect or difference when none exists is called

Answer 23

Type I error (alpha)

false positive

Question 24

Stating that there is not an effect or difference when one exists

Answer 24

Type II error (beta)

false negative

Question 25

range of values within which the true mean of the population is expected to fall, with a specified probability

Answer 25

confidence interval

Question 26

If the 95% CI for a mean difference between 2 variables includes 0, then

Answer 26

there is no significant difference and H0 is not rejected

Question 27

If the 95% CI for odds ratio or relative risk includes 1, then

Answer 27

H0 is not rejected

Question 28

If the CIs between 2 groups do not overlap, then

Answer 28

statistically significant difference exists

Question 29

If the CIs between 2 groups overlap, then

Answer 29

usually no significant difference exists

Question 30

prioritization of positive effects over negative effects (esp in hospice care) is known as

Answer 30

principle of double effect