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Flashcards in Module 8 & 9 Deck (17)
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1

Define "Confounding"

Confounding occurs when a variable is related to the exposure AND either causes or prevents the outcome

2

What is "Stratification"?

Stratification is a way to address confounding by separating out participants based on the confounding variable and analyzing them separately

3

What are the drawbacks of stratification?

It is difficult to stratify multiple data when multiple confounders are present. The process of stratification reduces sample size, thus decreasing power.

4

List three alternatives to stratification in order to address confounding

Randomization, Matching, Multivariable Statistical Adjustment

5

What is "Randomization"?

Randomly assigning individuals to exposure groups. Used only in interventional study designs

6

What is "Matching"?

Matching individuals in both test and control groups based on exposure to potential confounding variables. Used in "Case/Control" studies. Requires prior knowledge of confounding variables

7

What is Multivariable Statistical Adjustment?

A statistical method for consideration of confounding variables to utilize AFTER study participants are selected. Used in a variety of study types

8

What is Multivariable Regression

A complicated statistical adjustment used for addressing confounding variables in a study. The result of Multivariable Regression is the "adjusted estimate"; a statistical estimate of the effect of that exposure on the outcome.

9

What is the "adjusted estimate"?

The result of Multivariable Regression is the "adjusted estimate"; a statistical estimate of the effect of that exposure on the outcome.

10

List three type of logistical regression and what data-set they are typically used for

Multivariable Logistic Regression - used for CATEGORICAL variables Multiple Linear Regression - Used for CONTINUOUS variables Multivariable Cox Regression - Used for Time-to-Event data

11

What is the "correlation coefficient", which type of statistical analysis is it associated with, and what information does it provide?

Multiple Linear Regression yields a "Correlation Coefficient." (r). r = 0 = no correlation, r > 0 = positive correlation, r < 0 = negative correlation. Doesn't relate to slope, only estimates how well X can predict Y. Sometimes referred to as R^2

12

What is the "Median Survival Time"?

On a Kaplan-Meier Survival Curve, it is the time on the X-axis where the KMSC crosses 0.5 on the survival function axis. (i.e., 50% probability of the outcome)

13

Describe "Censoring" and how it relates to the Kaplan-Meier Survival Curve.

Censoring is what gives the KMSC it's unique step-shape. It occurs when participants achieve the event under study or are lost to followup.

14

List for key considerations for interpreting Klan-Meier survival curves.

What defines the beginning of follow-up? How long was follow-up conducted? Are their differences between cohorts that might lead to differences in censoring? Is there a difference in the Median Survival Times between groups?

15

What is the log-rank test?

A statistical test used to see if there are statistically significant differences between groups. Mentioned in connection with interpretations of Kaplan-Meier Survival curves and Median Survival Times

16

What is "Cox Regression"?

A statistical technique that allows for multivariable analysis of time-to-event data. Commonly seen in clinical trials and cohort studies.

17

What is a "Hazard Ratio"?

The product of Cox Regression. Hazard Ratios reflect the relative rate of an event in one group vs. another. A HR = 1.0 = no difference, HR > 1 suggests harm, HR < 1 suggests benefit.