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65 Cards in this Set

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Categorical vs Continuous Date types? (what are the sub categories?)
Categorical: Nominal (hair color) and Ordinal (pain scale, high med., low)
Continuous: Interval (rank/order, temp, but no true zero), Ratio (has true zero, eg mass in kg)
What is dichotomos data?
two mutually exclusive possibilities
what is discrete data?
integers only
When use chi test? (ie what data type?)
categorical - hair color, etc
When use t-test?
with continuous data (blood pressure levels, etc)
This is calculated as c/(a+c)
False-negative error rate
This is the ability of a test to detect a disease when it is present
Sensitivity
This defines normal and abnormal test results
cutoff point
this is the tendency of a measure to be correct on average
accuracy
this is calculated as a/(a+c)
sensitivity
this is the ability of a test to exclude a disease when it is absent
specificity
this is a nondifferential error
random error
the closer this is to the upper left corner of an ROC curve, the better it is
cutoff point.
This is an analytic study in which the outcomes were deterimed prior to the exposure being determined
Case-control
this is an analystical study in which the outcomes were determined some time after the exposure/intervention was determined.
cohort/follow-up
an analytical study in which the population is surveyed at a single point in time for risk factors and disease outcomes
cross-sectional
an analytical study in which the intervention is randomly allocated
randomized control trial
What measure of association do you use in case-control studies?
Odds Ratio
What is performance bias?
It is systematic differences in care the provided to intervention and control group.
What is co-intervention?
When members of comparison group change habits that change risk of outcome.
What is effect size?
The difference in outcomes observed between treatment/control groups.
What is the difference between reliability and validity?
Reliablity is the degree to which measurements are reproducible. Validity is the degree to which results = true values.
What is internal validity? External?
Internal = the freedom from bias, random error, confounding variables
External = the generalizability of the measurements (relevance/applicability)
What is retrieval bias?
Investigator conducting review selects studies that support hypothesis (or are otherwise biased)
What is reporting bias?
Investigator of original study only report data that supports view (e.g. drug sponsored). The tendency to under-report unexpected or undesirable experimental results while being more trusting of expected/desirable results.
What is publication bias?
Publishing only studies with statistically significant results make it to the journals.
Can confounding be transmitted into a meta analysis?
Yes
What's up with the funnel plot? Why does it narrow at the top?
Bc the y-axis is the size of the study and as you go up, variance decreases as you improve statistical power.
What is systematic error?
When variations in measurement are predictable/biased (i.e. there is consistent variablility between 'true' and 'study' samples). Results in reduced accuracy.
What is random error?
It is 'noise' that reduces precision of measurements (fluctuations due to sampling variability around a true value).
What is measurement bias?
When analysis of outcomes is influenced by knowledge of treatment group
What is confounding?
It is the influence of variables that may be responsible for association/effect.
What is the Hawthorne Effect?
When people act differently when they know they are being watched.
What is allocation bias?
When investigators choose non-random method of assignment
What is recall bias?
people are more likely to think/recall previous risk factors associated with adverse event than those who are unaffected
What is healthy use bias?
When pts who adhere to preventive therapies may be more likely to engage in a broad spectrum of healthy lifestyle - not representative of general population.
How is Kappa Coefficient used to reduce error?
It's an estimate of inter-rater reliability
What is the definition of risk?
The proportion of persons who are unaffected at beginning of a study period but undergo risk event during study period (proportion affected of susceptible known population over time)
What are two examples of probability?
Inicidence (risk) and prevalence
What is the equation for odds?
p/(1-p)
The probablity of event divided by probability of no event.
What is an example of a study that uses odds ratios?
Case-control
What is the equation for risk ratio (relative risk)?
(incidence in exposed)/(incidence in unexposed)
What is the equation for odds ratio?
(odds of exposure in cases)/(odds of exposure in controls)
Set up a table and calculate risk ratios and odds ratios
Now
How do you calculate relative risk difference (RRD)?
(EER - CER)/(CER)
How do you calculate Absolute Risk Difference?
CER-EER
How does interval data differ from ratio data?
Interval data does not have a true zero - e.g. celsius
Ratio data has a true zero - e.g. kilograms.
How do you calculate Beta-error? What is Beta usually set at?
It's power; Simply, Power = 1-Beta. Usually set at 0.2 or 20%
When calculating specificity and sensitivity, is it on left or right column?
1. Sensitivity is on the left
2. Specificity is on the rt
Set up a table and calculate sensitivity and specificity
do it
What is the definition of sensitivity? How is it used in screening methods?
Its the probability that a person with disease will have a positive result. Used to screen IN diseases with low prevalence.
What is the definition of specificity? How is it used in screening methods?
It's the probability that a person without disease will have a negative result. Used for confirmatory test after a positive screen test.
What is the difference between a screening test and a diagnostic test?
Screening = detect disease in asymptomatic individuals
Diagnostic test = confirm or rule out suspected disease in symptomatic individuals
The likelihood of disease given a positive or negative test depends on:
Disease prevalence and the test's properties
What the definition of a positive likelihood ratio?
It is how many times more (or less) likely a positive test result is found in diseased, as compared to non-diseased, individuals:
(True positive rate)/(false positive error rate)
What is the def of a negative likelihood ratio?
How many times more (or less) likely a negative test result is found in non-diseased, as compared to diseased, individuals (false neg error rate)/(true neg rate)
What is the def of PPV?
Positive predictive value is the probability of disease given a positive test resutl
What is NPV?
The negative predictive value is the probability of no disease given a negative test result.
With respect to PPV and NPV, as prevalence goes up, does PPV and NPV go up or down?
PPV goes up and NPV goes down
What is primary prevention?
Measures/activities to prevent disease from occurring
What is secondary prevention?
Early interventions/screens of disease to prevent progression or reduce disability
What is tertiary prevention?
Treatment/rehabilitation once disease has occurred to minimize sequelae or recurrence.
What is spectrum bias?
Study population has higher disease prevalence and/or severity than typical population
What is lead time bias?
Detecting disease earlier appears to increase duration of survival fictitiously.
What is length time bias?
Screening more likely to catch case that progresses slowly from disease onset to symptoms.