Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/78

Click to flip

78 Cards in this Set

  • Front
  • Back
define sensitivity
# of true positives divided by all people with disease
define specificity
# of true negatives divided by all people without disease
positive predictive value
# of true positives divided by all people who tested positive
negative predictive value
# of true negatives divided by all people who tested negative
what characteristic is desirable for a confirmatory test?
high specificity
what characteristic is desirable for a screening test
high sensitivity
define odds ratio
estimate of relative risk because don't have incidence data (case-control)
define relative risk
incidence of disease in person exposed to risk factor / incidence of disease in person not exposed to risk factor
what type of studies use odds ratio?
case-control studies
what type of studies use relative risk?
cohort studies
how are samples chosen for a case-control study
chosen based on presence (cases) or absence (controls) of disease
what type of information is being collected in a case-control study?
risk factors
how are samples chosen in a cohort study?
presence or absence of risk factors
what effect does a meta-analysis have on limitations or bias in studies?
can't overcome limitations
what does a meta-analysis try to achieve?
greater statistical power
what type of information is being collected in a cohort study?
development of disease
define clinical study
compares therapeutic benefits of 2 or more treatments or treatment/placebo
bias: subjects permitted to choose whether to go into drug group or placebo group rather than being assigned randomly
selection bias
knowledge or presence of disorder alters remembering by subjects (i.e. parents of kids w/ birth defects)
recall bias
subjects who volunteer to be in a study are not representative of population being studied
sampling bias
information gathered at an inappropriate time
late-look bias
name 4 ways to reduce bias
blind studies, placebo responses (having control group), crossover studies, randomization
define crossover study
each subjects acts as own control (patient receives drug then later on receives placebo, and vice versa)
define prevalence
total cases in population at given time/total population
define incidence
new cases in population over a given time / total population at risk during time
is prevalence or incidence greater for chronic disease?
prevalence
is incidence or prevalence greater for acute disease?
incidence
what is the relationship between prevalence and incidence (mathematically)?
prevalence = incidence x disease duration
what factor do you need to account for in calculating incidence?
people previously positive for disease are no longer considered at risk
how do you mathematically calculate the false negative rate?
1-sensitivity
how do you mathematically calculate the false positive rate?
1-specificity
when does the odds ratio approximate the relative risk?
when the prevalence of the disease is not too high
define precision
how reliable is the estimate (are all values closer together?)
define accuracy
how close is the estimate to the true mean
what is the difference between random error and systematic error?
random error: reduced precision in test; systematic error: reduced accuracy in test
what is the relationship between mean, median, and mode in a gaussian distribution?
all are equal
what is a bimodal statistical distribution?
2 modal peaks - two distinct populations
what is the relationship between mean, median and mode in a positive skew
mean>median>mode
where is the tail of a positive skew?
to the right
what is the relationship between mean, median, and mode in a negative skew?
mean<median<mode
where is the tail in a negative skew?
on the left
define null hypothesis
hypothesis of no difference
define alternative hypothesis
hypothesis that there is a difference
define type 1 error
stating there is a difference where no exists
what greek letter defines type I error?
alpha
define p value
probability of making type 1 error (say there's a difference when there isn't)
define type II error
stating there is no difference where one exists
what greek letter defines type II error?
beta
what is the mathematical equation for power?
1-beta
define power
probaiblity of rejecting null hypothesis when it is indeed false
how do you increase the power?
increase sample size
what 3 factors does power depend on?
total number of end points experienced by population, difference in compliance between treatment groups, size of expected effect
how many people are within 1 standard deviation
68%
how many people are within 2 standard deviations
95%
how many people are within 3 standard deviation?
99.7%
what does SEM stand for?
standard error of the mean
what is the mathematical equation for standard error of the mean?
standard deviation/square root (sample size)
what is greater, standard error of the mean or standard deviation?
standard deviation
what is the relationship between sample size and standard error of the mean
SEM decreases as n increases
definition: range of values in which a specified probability of the mean of repeated samples would be expected to fall
confidence interval
if the 95% CI for a mean difference includes 0, what does this signify?
no significant difference, null hypothesis not rejected
if the 95% CI for an odds ratio or RR includes 1, what does this signify?
null hypothesis is not rejected
evaluate presence of statistically significant differences between 2 groups
T-test
test that evaluates the presence of statistically significant differences between 3 or more groups
ANOVA (analysis of variance)
analyze categorial data or compare proportions
chi squared
what is the mathematical expression for coefficient of determination
r(squared)
between what 2 integers is r always located?
-1 and 1
what does the absolute value of "r" indicate?
strength of correlatoin between 2 variables
what is already known when calculating sensitivity?
person has disease
what is already known when calculating specificity?
person doesn't have disease
what is already known when calculating PPV
preson already tested positive
what is already known when calculating NPV
person already tested negative
what factors does prevalence have a relationship with?
positive predictive value, negative predictive value
what is the relationship with prevalence and PPV
higher the prevalence, higher the PPV
what is the relationship between prevalence and NPV
lower the prevalence, higher the NPV
how do you calculate confidence interval
mean of sample plus/minus (Z score * SEM). 95% CI (z=2). 99.7% CI (z=3)
what is the relationship between accuracy, precision, and the width of the CI
wider the CI, the less precise, the more accurate (wider CI more likely to contain mean)
how to calculate an odds ratio
(person with risk factor that has "disease" x person without risk factor that does not have "disease) / multiple two opposites