Statistics

Question 1

A systemic error where a study group is not representative of a population.

Answer 1

Selection/Sampling Bias

Question 2

People who volunteer are not the same as the general population.

Answer 2

Healthy User Effect

Question 3

When the sample is taken not from the general population, but from a subpopulation.

Answer 3

Berkson Bias

Question 4

People who choose to be in a study are different from people who do not; research only makes conclusions about those who choose to take part in the study.

Answer 4

Non-Respondent Bias

Question 5

Sicker people are more likely to be in studies; biased toward sicker cases.

Answer 5

Ascertainment Bias

Question 6

Those with more severe sickness are least likely to be included in the study; harder to access or more likely to be decreased; sample biased to less sick cases.

Answer 6

Late-Look Bias

Question 7

People who choose to be in a study are different from people who do not > study participants who dropped out/died were not accounted for analysis > drop-outs/deaths may be different from those who stay/survive.

Answer 7

Attrition Bias

Question 8

Statistical analysis that keeps drop-outs in the same groups; drop-outs counted as non-responders.

Answer 8

Intent-To-Treat Analysis

Question 9

What are examples of selection/sampling bias?

Answer 9

• Healthy User Effect
• Berkson Bias
• Non-respondent Bias
• Ascertainment Bias
• Late-Look Bias
• Attrition Bias

Question 10

Information is gathered in a way that distorts the association between exposure and outcome; how the data are collected will affect the data that are obtained. For example, leading questions and Hawthorne Effect.

Answer 10

Measurement Bias

Question 11

A subject’s behavior is altered because they are aware they are being observed.

Answer 11

Hawthorne Effect

Question 12

What are some examples of measurement bias?

Answer 12

• Recall Bias
• Observer Bias
• Placebo Effect

Question 13

People do not accurately remember what happened in the past; they make things up or base things on the present circumstances.

Answer 13

Recall Bias

Question 14

Person making the assessment/measurement assumes an outcome based on their previous experience.

Answer 14

Observer Bias

Question 15

Patient in the comparison/control/placebo group believes that they are in the treatment/intervention/drug group, and reports accordingly.

Answer 15

Placebo Effect

Question 16

Researcher unintentionally acts in a way that influences the outcome.

Answer 16

Expectancy Bias (Pygmalion Effect)

Question 17

Tendency to only publish results with “positive” or significant outcomes.

Answer 17

Publication Bias (File Drawer Effect)

Question 18

The relationship between exposure and outcome is not a perfectly linear one; often there are other things that influence the association between the exposure and the outcome.

Or when the association between an exposure and an outcome is altered by the presence of an extraneous variable.

Answer 18

Confounding Bias

Question 19

Overestimation of survival duration due to earlier detection by screening (ex. over-diagnosis/over-detection).

Answer 19

Lead-Time Bias

Question 20

What are some features that may be included in a Randomized Control Trial?

Answer 20

• Placebo
• Standard of (Usual) Care
• Wait-List Control

Question 21

When a treatment of benefit already exists, and we are looking for a better treatment - “Does this work better than what already exists?”

Answer 21

Standard of (Usual) Care

Question 22

Is a group of participants included in an outcome study that is assigned to a waiting list and receives intervention after the active treatment group. This control group serves as an untreated comparison group during the study, but eventually goes on to receive treatment later.

Answer 22

Wait-List Control

Question 23

What are the phases of a clinical trial?

Answer 23

SWIM

1 - Safety
2 - Work (Does it work?)
3 - Improve
4 - Marketing

Question 24

Prevent the onset of illness or injury before the disease process begins. Prevents incidence.

Answer 24

Primary (Universal) Prevention

Question 25

Lead to early diagnosis and prompt treatment of a disease, illness or injury; to prevent more severe problems developing.

Answer 25

Secondary Prevention

Question 26

Aimed at rehabilitation following significant illness. Reducing negative impacts, increasing quality of life.

Answer 26

Tertiary Prevention

Question 27

Collects all possible studies related to a given topic and design, and reviews and analyzes their results.

Answer 27

Systematic Review

Question 28

Go a step further and statistically analyze the results from all the studies.

Answer 28

Meta-Analysis

Question 29

If the diamond on a forest plot is sitting on or touches the line, it is considered?

Answer 29

Not Significant

Question 30

If the diamond on a forest plot is to the left of the line, it is considered?

Answer 30

Lower Risk

Question 31

If the diamond on a forest plot is sitting to the right of the line, it is considered?

Answer 31

Higher Risk

Question 32

A measure of how different the studies are, and if that difference is outside that of expected chance.

Answer 32

Heterogeneity

Question 33

If a p value is > 0.05, what does that mean for heterogeneity?

Answer 33

Low Heterogeneity; it is the opposite if less than

Question 34

On a funnel plot, if there are more symmetric dots clustered around the line, that means there is?

Answer 34

Less Publication Bias

Question 35

What is the eligibility criteria for a systematic review or meta-analysis?

Answer 35

PICOS

P - Population
I - Interventions
C - Comparator
O - Outcomes
S - Study Designs