Cards Flashcards
Biostatisticians prefer type ______ errors to type _____ errors.
Biostatisticians prefer type I errors to type II errors.
Failing to reject the _______ hypothesis (Type II error) is a more conservative statement than rejecting the null hypothesis because it errs on the side of caution and can usually be rectified with further studies.
Null
What is the symbol for sample standard deviation?
s
What is the symbol for population standard deviation?
σ
The higher the value of n (sample size) and thus the higher the degrees of freedom, the closer a ___ distribution resembles a ___ distribution.
The higher the value of n (sample size) and thus the higher the degrees of freedom, the closer a t distribution resembles a z distribution.
At around an n of ___, the t distribution is close enough to the z distribution that it makes no significant difference.
30
What is the formula for degrees of freedom?
n - 1 (Where n=sample size)
In hypothesis testing, rejecting a true null hypothesis is called ______ error.
In hypothesis testing, rejecting a true null hypothesis is called type I error.
In hypothesis testing, failing to reject a false null hypothesis is called _____ error.
In hypothesis testing, failing to reject a false null hypothesis is called type II error.
_________ is the measure of new cases of a disease.
Incidence
__________ is the number of new cases of a disease in a population over a specified time period.
Cumulative incidence
__________ is the number of new cases of the disease during person-time of observation where time is measured as the amount of time people are followed or exposed, ranging from before the onset of disease to the end of follow-up.
Incidence rate
_________is the number of existing cases of a disease during a given time period.
Prevalence
___________ is the proportion of the population that is diseased at a single point in time, such as a specific calendar date.
Point prevalence
_________ is the proportion of the population that is diseased during a specific duration of time, such as during a specific year.
Period prevalence
_______ is a situation in a community in which there is a consistent elevated rate of a certain disease.
Endemic
______is an increase in the number of cases of disease in a community, above what is expected.
Epidemic
___ is a worldwide epidemic.
Pandemic
______are calculated by dividing one number by another but the numerator does not need to be a subset of the denominator as they are two distinct quantities. Ex. Men:women
Ratio
______are calculated by dividing one number by another, where the numerator is a subset of the denominator. Ex: number of men/total population
Proportion
_____ are calculated by dividing one number by another, and additionally have a time component as a part of the denominator. Ex: The number of people who developed influenza in 2017.
Rate
What are the two overall types of epidemiologic study designs?
Descriptive and analytic
______ studies are generally observational, whereas ______ studies can be both interventional (experimental) and observational.
Descriptive Analytic
This type of descriptive study is used to alert people of a new illness or association with an illness. They are usually reports of only people with the condition of interest.
Case studies and case reports
These type of descriptive studies include people who are representative of a given population. They are not selected on the basis of illness or exposure and can be used to determine initial associations and to identify the prevalence of either exposure or illness in a group.
Cross-sectional studies
This type of descriptive studies are used to describe populations. The data are not analyzed on the individual level, but rather on the aggregate level.
Ecological studies
In _______, group-level data are used to report on individuals. This type of mistake occurs in ecological studies.
Ecological fallacy
In this type of analytic study, people are selected based on whether they have or do not have a disease and then the researchers proceed to look back over time to see if people had different rates of exposure.
Case-control
This type of study is good for rare diseases with long latency periods.
Case-control
This analytic study type selects people on the basis of exposure and determines if people develop disease at different rates.
Cohort studies
This type of study is good for rare exposures.
Cohort studies
When a study follows individuals into the future.
Prospective
When a study looks back in time
Retrospective
This type of analytic study allows researchers to calculate incidence.
Cohort studies
People who have disease at the time point when the study begins are excluded from cohort studies. These cases are known as _______ cases.
prevalence
This type of analytic study tests an intervention that is given by the researcher to two or more groups.
Randomized controlled trial (RCT)
________ is when people are randomly assigned to groups in a randomized control trial.
Randomization
In _______ blinded studies, participants don’t know what group they are in and in ______ blinded studies, neither participants nor researchers know which group participants are in.
single double
These analytic studies pool the results of multiple independent studies with established criteria to identify the evidence for associations.
Meta-analyses and systematic reviews
The hierarchy of types of study designs by amount of evidence collected goes:
expert opinion -> case series and case reports -> cross-sectional -> case-control -> cohort ->RCT -> systematic reviews and meta-analyses
expert opinion -> case series and case reports -> cross-sectional -> case-control -> cohort ->RCT -> systematic reviews and meta-analyses
The three types of descriptive observational study designs are?
case reports, case series, and cross-sectional
The two types of experimental study designs are?
randomized controlled trials and non-randomized trials
The three types of analytical observational studies are?
Cohort, case-control, and cross-sectional
Draw a 2x2 table for epidemiological calculations
outcome and no outcome go at top for column headers and exposure and no exposure go on left for row headers. outcome in exposed is A, outcome in unexposed is C, total outcome is A+C, no outcome among exposed is B, no outcome and not exposed is D, and total with no outcome is B+D. Total exposed is A+B, total unexposed is C+D, and total is A+B+C+D
_______ is the measure of the magnitude of an association between an exposure and a disease that is used in cohort studies. It is a ratio of the risk (incidence) of disease in the exposed tot eh risk in the nonexposed.
Relative risk (RR)
The formula for relative risk is?
RR=(Risk [incidence] of outcome in the exposed)/Risk [incidence] of outcome in the nonexposed. If using a 2x2 table, this appears as A/(A + B) divided by C/(C + D)
An RR or OR of _ means there is no association between the exposure and the outcome. The risk or odds in the exposed equals the risk or odds in the nonexposed.
1
An RR or OR of _ means the exposure increases the risk of the outcome. The risk or odds in the exposed is greater than the risk or odds in the nonexposed.
> 1
An RR or OR _ means the exposure decreases the risk of the outcome. The risk or odds in the exposed is less than the risk or odds in the non-exposed. This indicates that the exposure is a protective factor.
<1
____ is a systematic error as compared to an error attributable to chance alone. It can cause an error in the estimation of an association between an exposure and an outcome.
Bias
This type of bias results from procedures used to select participants into a study. This bias results in a different outcome from what would have been obtained from the entire population targeted for the study.
Selection bias
Selection bias most likely occurs in _______ or _____ studies because the exposure and outcome have occurred at the time of study selection. It can also occur in prospective cohort studies and experimental studies from differential loss to follow-up because this affects which subjects are “selected” for analysis.
case-control or retrospective cohort
This type of bias arises from systematic differences in the way information on exposure or disease is obtained from the study groups.
Observation bias/information bias
This type of bias involves inaccurate reporting of past events
recall bias
This type of bias may include the effects of the interviewer’s body language, voice, or demeanor on the response; it’s the most difficult type of bias to account for.
Interviewer bias
This type of observational bias happens when participants are incorrectly classified into the wrong population. It distorts the link between exposure and outcome. It can result from participants being incorrectly classified as exposed or unexposed or having the outcome or not having the outcome.
Misclassification error
Differential misclassification is bias that is ______different between groups.
different
Nondifferential misclassification bias is bias that is _____ across groups.
Equal
___________ occurs when a researcher is evaluating the relationship between an exposure and an outcome, but a third variable, which is associated with both the exposure and the outcome, distorts the finding.
Confounding
Methods to prevent confounding and to manage confounding during the analysis stage include:_____, _______, ______,______, ______, and conducting__________.
randomization, restriction, matching, standardization, stratification, and conducting multivariable analysis