# Biostatistics

FlashcardsHow are confidence intervals calculated ?

Using the number of observations and the standard deviation

Was a type I error ?

A type I error also known as a alpha error is incorrectly concluding that a statistical significant difference in a data set has been observed

What is a type II error ?

A type II error also known as a beta error is making an incorrect conclusion that there is no statistically significant difference in a data set

What is the definition of power in biostatistics ?

Power refers to the ability of an experiment to detect a true difference in experimental arms

When is logistic regression used ?

Modeling the dichotomous outcomes

When is linear regression used ?

Modeling continuous outcomes

What are the 2 common time-to-event analyses used in oncology ?

Kaplan-Meier and Cox Proportional Hazard Analysis

What is the standard error of the meeting ?

It describes how much variability one can expect when measuring the mean from several different samples

What is the definition of incidence ?

The incidence is the number of new events that have occurred in a specific time interval divided by the total number of people at risk at the beginning of the time interval

What is the definition of prevalence ?

Prevalence is the number of people with a specific disease at a given point in time divided by the total number of people at risk at that point in time

What is the definition of relative risk ?

RR if the incidence in exposed people divided by incidence in unexposed people

What is the definition of an odds ratio ?

An odds ratio is the odds that an individual with a particular disease who has been exposed to a risk factor divided by the odds that the control group was also exposed

When is an odds ratio used ?

It is usually used in the case control studies

What is a hazard ratio ?

A hazard ratio is the effect estimate generated by a time-to-event analysis.

What is the number needed to treat a reciprocal of ?

It is the reciprocal of absolute risk difference

What is it a kappa statistic ?

Kappa Statistics are used to measure interobserver agreement such as comparing Ki-67 values across different tissue samples and assays

What is the definition of sensitivity ?

Sensitivity is the number of people with a confirmed positive test who have a disease divided by all the people who have the disease

What is the definition of specificity ?

Specificity refers to the number of people with a confirmed negative test who do not have any disease divided by the number of patients who do not have the disease

What is a positive predictive value ?

PPV for a test represents the likelihood a patient with a positive test has the actual disease

What is a negative predictive value ?

NPV represents the odds of person with a negative test is free of the disease

What is a likelihood ratio ?

The likelihood ratio represents a measure of the odds of having a disease relative to the prior probability of the disease

What is a confidence interval ?

A confidence interval provides a range in which the true value likely lies for a hazard ratio.

What are the bounds of a confidence interval ?

95%

What is the difference between a hazard ratio and a relative risk ?

Relative risk is a snapshot in time, usually the end of a study while the hazard ratio is the dynamic result

What is the confidence interval?

The range of outcomes you would find the hazard ratio if the experiment were extrapolated out to the entire population at risk

What is the difference between prevalence and incidence?

Prevalence is a static variable while incidence is the annual diagnostic rate

What is the difference between sensitivity and specificity?

Sensitivity is for ruling out a disease while specificity is for ruling in a disease

What is the usual p-value that is used to reject a null hypothesis?

5%

Why is a subset analysis not always a reliable way to draw a conclusion from a study?

It may not be powered enough