Biostats

Question 1

Case Control Study

Answer 1

Looks for prior exposure or risk factor and asks ‘what happened?’ observational and retrospective (odds ratio)

Question 2

Cohort Study

Answer 2

compares a group with a given exposure or risk factor to a group without. Can be prospective or retrospective relative tisk

Question 3

What do cohort studies look to answer?

Answer 3

does an increased exposure increase the likelihood of disease? ‘Smokers has a higher risk of developing COPD than nonsmokers’

Question 4

Cross-sectional study

Answer 4

collects data from a group of people to assess frequency of disease (and related risk factors) * at a particular point in time* (disease prevalence)

Question 5

T or F. Cross-sectional studies can show risk factor association with disease but does not establish casualty

Answer 5

T.

Question 6

What is the study sample in a phase I clinical trial?

Answer 6

small no. of healthy volunteers

Question 7

What is the purpose of a phase I clinical trial?

Answer 7

assesses safety, toxicity, and pharmacokinetics (ADME)

Question 8

What is the study sample in a phase II clinical trial?

Answer 8

small no. of patients with the disease of interest

Question 9

What is the purpose of a phase II clinical trial?

Answer 9

assesses treatment efficacy, optimal dosing, and adverse effects

Question 10

What is the study sample in a phase III clinical trial?

Answer 10

large no. of patients randomly assigned

Question 11

What is the purpose of a phase III clinical trial?

Answer 11

compares new treatment to the current standard of care

Question 12

What is the study sample in a phase IV clinical trial?

Answer 12

post-market surveillance

Question 13

What is the purpose of a phase IV clinical trial?

Answer 13

detects rare or long-term AEs

Question 14

2x2 Table

Answer 14

Question 15

What is sensitivity?

Answer 15

The proportion of all people with disease who test positive (or the probability that a test detects disease when it is present)

=TP/(TP+FN)

=1-false negative rate

Question 16

T or F. A Sensitivity approaching 1 is good for RULING OUT disease

Answer 16

T. SNOUT

Question 17

What is specificity?

Answer 17

Proportion of all people without disease who test negative

=TN/(TN+FP)

Question 18

What is specificity good for determining?

Answer 18

ruling IN disease. SPIN

It is used as a confirmatory test a positive screening test

Ex. HIV Testing. Screen with ELISA (sensitive, high false-positive rate though). Follow up with a Western Blot (specific)

Question 19

What is positive predictive value?

Answer 19

Proportion of positive test results that are true positives

=TP/(TP+FP)

Question 20

What is negative predicitive value?

Answer 20

Proportion of negative test results that are real negatives

=TN/(TN+FN)

Question 21

Which predictive value (positive or negative) increases with increased disease prevelance?

Answer 21

Positive

NOTE: Unlike specificity and sensitivity, PPV and NPV vary with prevelance. If prevelance is low, even tests with high sensitivity or specificity will have low PPV)

Question 22

What is the difference between prevalence and incidence?

Answer 22

Prevalence is the no. of total cases in a population/population whereas incidence is the no. of NEW cases/population

Question 23

Shortcut eqn for prevalence

Answer 23

=incidence X disease duration

Question 24

Eqn for odds ratio (for case-control studies)

Answer 24

OR= (a/b)/(c/d) or ad/bc

Question 25

Eqn for relative risk (for cohort studies)

Answer 25

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

Question 26

What is attributable risk?

Answer 26

the probability of getting a diseasein the exposed group divided by the probability of getting a disease in the unexposed group (e.g. smoking causes 1/3 cases of pneumonia) = a/(a+b) - c/(c+d)

Question 27

What is absolute risk reduction?

Answer 27

reduction in risk associated with a treatment compared to a placebo = c/(c+d) - a/(a+b)

Question 28

Number needed to treat and No. needed to harm eqns

Answer 28

Number needed to treat= 1/absolute risk reduction No. needed to harm= 1/attributable risk

Question 29

T or F. A systematic error reduces precision (consistency and reproducibility) in a test

Answer 29

F. It reduces accuracy (trueness of the measurements) in a test

Question 30

What is late-look bias?

Answer 30

gathering info at an inappropriate time (e.g. survey in a fatal disease where only the living can participate)

Question 31

What is Berkson's bias?

Answer 31

A form of selection bias that causes hospital cases and controls in a case control study to be systematically different from one another because the combination of exposure to risk and occurrence of disease increases the likelihood of being admitted to the hospital.

Question 32

What is lead-time bias?

Answer 32

When early detection is considered extended survival even though the timeline/progression of the disease is the same

Question 33

What is a pygmalion effect?

Answer 33

When a researcher's belief in the efficacy of a treatment changes the outcome of the treatment

Question 34

What is the Hawthrone effect?

Answer 34

Occurs when the group being studes changes its behavior owing to the knowledge of being studies Dr. Hawthrone is watching you

Question 35

What is the eqn for SEM (standard error of the mean)?

Answer 35

stand. dev/ sqrt(n) SEM decreases as n. increases

Question 36

Positive skew of normal Gaussian distribution

Answer 36

Wave to the right mean \> mode \> median

Question 37

What is a type 1 error (a)?

Answer 37

stating that there is an effect or difference when none exists (mistakenly accepting the hypothesis and not the null) (you sAw a difference that wasn't really there) NOTE: If p is less than 0.05 then there is less than 5% chnges that the data will show something that is not really there

Question 38

What is a type II (beta) error?

Answer 38

Accepting the null inappropriately you were Blind to a difference that did exist

Question 39

What is Power?

Answer 39

the probability of rejecting the null when it is in fact false

Question 40

What things affect power?

Answer 40

Sample size. Increased sample size= increased power

Question 41

Interpreting CI

Answer 41

If a 95% CI for a mean difference between 2 variables includes 0, then there is no significant difference and Ho is not rejected If a 95% CI for odds ratio or relative risk includes 1, then there is no significant difference and Ho is not rejected

Question 42

When is parental consent not required?

Answer 42

1. Patient is emancipated (married, has children, or is in the military) 2. emergencies 3. when giving contraceptives 4. treatment involving STDs, during pregnancy, or in the management of drug addiction

Question 43

Surrogates can act in the interest of a patient that is incapacitated or has not given an oral or written advance directive. What is the order of priority in family members?

Answer 43

1. Spouse 2. Adult children 3. Parents 4. Siblings 5. Other

Question 44

What are some exceptions to confidentiality?

Answer 44

1. Potential harm to others or self 2. Suspicion of abuse 3. Impaired automobile drivers 4. Serious communicable diseases

Question 45

What is the Tarasoff decision?

Answer 45

law requiring physicians to directly inform aand protect potential victims from harm