Exam

Question 1

Describe: case-control studies

Answer 1

People w/ & w/out condition are compared on exposures/ interventions they had in the past

• Prevalence
• Controls are selected based on prior design
• Starts w/ outcome & looks back at exposure

Question 2

Describe: cohort studies

Answer 2

Groups that have an exposure or receive an intervention are compared to others who do not

• Incidence
• Disease vs. no disease, followed over time
• Exposure 1st

Question 3

Describe: cross-sectional studies

Answer 3

• Prevalence
• Exposure & outcome are measured at same time
• “Snapshot”. Ex = survey

Question 4

What type of research questions do RCTs address?

Answer 4

Prevention, screening, diagnostic accuracy, therapy

Question 5

Define: incidence

Answer 5

# of new occurrences in a population over a period of time 
- Conveys info about the risk of contracting the disease

Question 6

Define: prevalence

Answer 6

Proportion who have a particular condition at a point in time
- Conveys info about how widespread the disease is

Question 7

Define: absolute risk

Answer 7

Risk of developing the disease over a time period in a group of people

Question 8

Define: relative risk (risk ratio)

Answer 8

Compares the absolute risk btwn groups of people

• Ratio = 1 = no difference
• Ratio < 1 = less risky
• Ratio > 1 = more risky

Question 9

Distinguish btwn observational vs experimental research designs

Answer 9

Both observe people & measure outcome

• Observational: lower level of evidence & the investigator does NOT specify intervention
• Experimental: investigator specifies intervention

Question 10

What type of study designs are considered to be observational?

Answer 10

• Ecologic
• Cross-sectional
• Case reports
• Case control
• Cohort

Question 11

Distinguish btwn controlled vs uncontrolled studies

Answer 11

Controlled:

• More than 1 group studied
• At least 1 comparison or control group is compared w/ experimental group

Uncontrolled:

• Single group studied
• No comparison

Question 12

Define: selection bias

Answer 12

People in comparison group may not be the same as the people in the experimental group

Question 13

How do you solve selection bias?

Answer 13

Randomization, allocation concealment

Question 14

Define: attrition bias

Answer 14

Differences in withdrawals or exclusions of people entered into a study, excluding pts from the analysis

Question 15

What does attrition bias lead to?

Answer 15

Overestimation of benefit & underestimation of toxicity

Question 16

How do you solve attrition bias?

Answer 16

“Intention to treat” analysis: Includes all study participants

Question 17

Define: performance bias

Answer 17

Differences in the care provided & exposure to other factors
- If providers know which group a participant is in, they may act differently towards that person

Question 18

How do you solve performance bias?

Answer 18

“Double” masking

Question 19

Define: information bias

Answer 19

Differences btwn groups in how data are collected or assessed

Question 20

How do you solve information bias?

Answer 20

• All groups must be measured in the same way

- “Double” masking

Question 21

What are the levels of evidence? From best to worst?

Answer 21

1. Systematic review of RCTs –> 2. Single RCT –> 3. Systematic review of controlled observation –> 4. Single controlled observation –> 5. Single uncontrolled observation –> 6. Physiologic studies –> 7. Unsystematic clinical observation

Question 22

Describe single controlled observation

Answer 22

Investigator compares 2 groups

Question 23

Describe single uncontrolled observation

Answer 23

Gathering many pt experiences

- Can’t demonstrate cause & effect

Question 24

Describe physiologic studies

Answer 24

Data about a mechanism of action

• May not reflect larger population
• Can’t demonstrate cause & effect

Question 25

Describe unsystematic clinical observation

Answer 25

Stories we hear (subjective reporting) - May not represent the broader experience - Lowest level of evidence

Question 26

Define: surrogate endpoint

Answer 26

Short term outcomes are measured

Question 27

Define: equipoise

Answer 27

Uncertainty about whether experimental intervention is better - Ethical requirement

Question 28

Define: placebo

Answer 28

Substance (or procedure) that looks, tastes, sounds, feels the same as experimental intervention - Controls for placebo effect - Allows for "masking" - Ethical in only certain settings

Question 29

Define: double masking

Answer 29

Participants & investigators don't know who is getting control or experimental intervention - Avoid bias

Question 30

Define: allocation concealment

Answer 30

Process used to ensure that the investigator does not know which group the person will be allocated

Question 31

Define: intent to treat analysis

Answer 31

Includes all study participants as part of the group @ which they were originally randomized whether or not they received or completed the intervention

Question 32

Describe: Ecologic studies

Answer 32

- Comparisons of groups instead of individuals | - Ex. rates of disease in groups/regions

Question 33

Give an example of an ecologic study

Answer 33

Relationship btwn laws against smoking & prevalence of smoking under age 16

Question 34

Describe: case-report/series

Answer 34

Uncontrolled observational studies | - Describes unusual or new occurrences

Question 35

Give an example of a cross-sectional study

Answer 35

Association btwn amt of time adults report watching TV & their BMI

Question 36

Which types of studies have "no randomization, bias, or self-selection"?

Answer 36

Case control & cohort

Question 37

Give an example of a case-control study

Answer 37

Mothers of children w/ & w/out spinal malformations were asked about diet during pregnancy

Question 38

Define: risk

Answer 38

Probability of suffering harm/loss | - Proportion of people experiencing the event of interest in a given time

Question 39

Define: harm

Answer 39

Physical or psychological injury/damage

Question 40

Define: benefit

Answer 40

Promotes well-being

Question 41

Define: screening

Answer 41

Testing for a disease in a population w/ no sx

Question 42

Distinguish btwn sensitivity vs specificity

Answer 42

- Sensitivity: How well the test finds the disease when it's present - Specificity: How well the test excludes the disease when it's not present

Question 43

Define: validity

Answer 43

Credibility or believability of research - Are the findings genuine? - External or internal

Question 44

Define: reliability

Answer 44

Repeatability of findings | - If the study was done a 2nd time, would you get the same results?

Question 45

Define: critical appraisal

Answer 45

Process of assessing & interpreting evidence by systematically considering its validity, results & relevance

Question 46

What is an abstract?

Answer 46

A condensed version of the full text of the paper, presenting the most important info

Question 47

What is included in an abstract?

Answer 47

- Context/background - Study purposes - Basic procedures - Main findings - Conclusions - New/important aspects of study

Question 48

Define: type I error (False positive)

Answer 48

Concluding that a tx works, when it actually does not work - Also called "alpha" - Rejecting the null, when it is true

Question 49

Define type II error (False negative)

Answer 49

Concluding that there is no evidence that a tx works, when it actually does work - Accepting the null, when it is false - Also called "beta" - Risk of type II error decreases as participants in study increases

Question 50

Define: innumeracy

Answer 50

Inability to deal comfortably w/ notions of # & chance - Affects informed consent & decision-making - Interferes w/ appraisal

Question 51

Define: framing effect

Answer 51

The presentation & context of info given affects how it is received

Question 52

Define: absolute risk reduction

Answer 52

Change in the risk of an outcome of a given tx in relation to a comparative one

Question 53

Define: relative risk reduction

Answer 53

The absolute risk difference, divided by the risk of the control

Question 54

Define: odds

Answer 54

``` # w/ event ÷ # w/out event - Expressed as decimal ```

Question 55

Define: odds ratio

Answer 55

Odds of an event in the exposed group ÷ odds of the event in the unexposed group - When odds ratio = 1, means no difference or no effect