Behavior Science

Question 0

Case control study

Answer 0

Observational, retrospective
Compare a group w disease to a group wo disease n look for exposure or risk factors
What happened
Measures odds ratio

Question 1

Cross sectional study

Answer 1

Data from a group at a particular point in time
What is happening
Measures Disease prevalence
Establish association not causality between risk factors and disease

Question 2

Cohort study

Answer 2

Observational, prospective or retrospective
Compares group w exposure to group wo n looks to see if exposure inc likelihood of disease
Who will develop or who did given exposure
Measures relative risk

Question 3

Four phases of clinical drug trial

Answer 3

Phase 1: small number of healthy, is drug safe, assess toxicity pharmakinetics

Phase 2: small number of patients, does it work, assess treatment efficacy and optimal dosage and side effects

Phase 3: large group randomized w control (placebo or best available), is it good or better, compare w existing treatment

Phase 4: post marketing surveillance, can it stay, long term adverse effects

Question 4

Sensitivity

Answer 4

Proportion of all people with disease who test positive, or the probability that a test detects disease when disease is present

Value approaching 100% is desirable for ruling out and indicate low false negative rate

Best for screening test

=TP / (TP + FN) = 1 - false negative

SN-N-OUT highly sensitive test when negative rules out disease

Question 5

Specificity

Answer 5

Proportion of all people without disease who test negative, or the probability that a test indicates non-disease when disease is absent

Value approaching 100% is desirable for ruling in disease and indicates a low-false positive rate

Best for confimrational diagnostic after positive screening

=TN / (TN+FP) = 1 - false positive
SP-P-IN highly specific test, when positive, rules in diseae

Question 6

Negative predictive value

Answer 6

Proportion of negative test results that are true negative

Probability that person actually is disease free given negative test result

=TN / (TN+FN)

High prevalence or pretest probability = low NPV

Question 7

Positive predictive value

Answer 7

Proportion of positive test results that are true positive

Probability that person actually has the disease given positive result

=TP/ (TP+FP)

High prevalence or pretest probability = high PPV

Question 8

Incidence rate

Answer 8

Number of new cases in a specified time period / population at risk during same time period

Looks at new cases

Question 9

Prevalence

Answer 9

Number of existing cases / population at risk

Looks at all current cases

Question 10

Odds ratio

Answer 10

Uses in case control studies

Odds that the group with the disease was exposed over the odds that the group w/o the disease was exposed

(a/c)/(b/d) = ad/bc where a and c are small (low prevalence of disease)
A is those with disease and exposed
C is those with disease and unexposed
B is those without disease and exposed
D is those without disease and unexposed

Question 11

Relative risk

Answer 11

Used in cohort studies

Risk of developing disease in exposed group over risk of developing disease in unexposed group

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

Question 12

Relative risk reduction

Answer 12

The proportion of risk reduction attributable to intervention as compared to control, RRR= 1-RR

Question 13

Attributable risk

Answer 13

The difference in risk between exposed and unexposed that is attributable to exposure

AR = a/a+b - c/c+d

Question 14

Absolute risk reduction

Answer 14

The difference in risk attributable to intervention as compared to a control (raw number percentage)

Question 15

Numbers need to treat

Answer 15

Number of patients who need to treated for 1 to benefit

=1/ARR

Question 16

Number needed to harm

Answer 16

Number of patients who need to be exposed to a risk factor to be harmed

=1/AR

Question 17

Selection bias

Answer 17

Non random assignment to participate in a study group

Study only look at inpatients, studying disease w early mortality but high loss to f/u, studying health workers and volunteers

Can be avoided w randomization

Question 18

Recall bias

Answer 18

Awareness of disorder alters recall by subjects, common in retrospective studies

Patients w disease recall exposure after learning similar cases

Avoided by decreasing time from exposure to follow u

Question 19

Measurement bias

Answer 19

Information is gathered in a way that distorts it

Hawthorne effect: groups who know they are being studied behave differently than if they didn’t know

Avoided with placebo control or blinding studies

Question 20

Procedure bias

Answer 20

Subjects in diff groups are not treated the same

Use sham methods to equalize study groups

Question 21

Observer bias

Answer 21

Researcher’s belief in efficacy of treatment changes outcome, self fulfilling prophecy

Avoid w double blind studies

Question 22

Confounding bias

Answer 22

When a factor is related to both exposure and outcome but not the causal pathway

Ex: pulmonary disease, coal mines, smoking

Corrected w crossover studies or matching pts w similar characteristics in study groups

Question 23

Lead time bias

Answer 23

Early detection is confused w increased survival, often seen w screening techs

Corrected w back end survival measurement, ex: adjust survival according to severity at time of diagnosis

Question 24

Null hypotheses

Answer 24

Hypothesis of no difference (no association between risk factor and disease)

Question 25

Alternative hypotheses

Answer 25

Some difference (association between disease and risk factor)

Question 26

Type1 error

Answer 26

Stating there is an effect or difference when there is none

Question 27

Type2 error

Answer 27

Stating there is no difference when there is none

Question 28

Meta analysis

Answer 28

Pools data and integrates results from several similar studies to reach overall conclusion

Limited by quality of individual studies or boas in study selection

Question 29

T -test

Answer 29

Check differences between means of two groups

Question 30

ANOVA test

Answer 30

Check differences between means of 3 or more groups

Question 31

Chi square test

Answer 31

Check differences between 2 or more percentages or proportions of categorical outcomes rather than means

Question 32

Stages of disease prevention

Answer 32

Primary: prevent disease occurrence, vaccinations

Secondary: screening, Pap smears

Tertiary: treatment, surgery or chemo

Quanternary: prevent unnecessary treatment

Question 33

APGAR score

Answer 33

Assess newborns at 1 min and 5 min on 10 pt scale

Based on appearance, pulse, grimace, activity, respiration

> 7 good, < 4 resuscitate