week 3 Flashcards
independent variable
the variable that is manipulated
presumed cause of an effect
what is being observed
dependent variables
the outcome of an intervention or exposure
measured variable used to determine the effects of the independent variable
outcome whose variation we seek to explain or account for by the influence of independent variables
confounder
factor other than the independent variable that influences the outcome
attribute variables
used to describe a sample
explanatory variables
variable that causally explains the relationship or outcome under study
predictors
variable that is causally related to a future outcome
internal validity
extent to which the study lacks bias
how well does the study support a causal relationship?
external validity
generalizability of results
can the results be applied to the population?
bias
a systematic error in the way a study is carried out that can lead to false conclusions
any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions tht are systematically different from the truth
threats to internal validity
history maturation testing instrumentation group assignment loss to follow up tmt crossover compensatory issues
threats to ext validity
subject selection
setting where research is conducted
time since study
causation
an outcome or event will occur as a result of a previous event
association
a statistical relationship btw two events that may or may not be causal
criteria for causation
exposire precedes outcome strong association biologically credible consistent with previous research dose-response relationship alternative expanations
direct measures
concrete values
indirect measures
abstract representations of quantities and/or characteristics
constructs
abstract variables that cannot be seen directly, but are inferred by measuring relevant behaviors that are observable
multidimensional
development of an instrument
categorical variables
nominal variables: counts, frequencies, percents
ordinal variables: rank ordered categories, quantitative analysis often ambiguous
numeric variables
interval and ratio variables
transforming scales
can change a numeric scare to categirocal but cannot change categorical to numeric
random error
chance variation in measurement
systematic error
results from an identifiable source
sources of error
inaccuracy, instrument inprecision, subject response bias
analytic procedures are used to quantify ____ due to random error
uncertainty
____ is dealt with in the design of the study anf through good measurement procedures
bias
variance
measure of variability or spread of observations in the sample
function of both true variability within the population and variability due to measurement error
reliability
degree to which a measurement procedure is repeatable
validity
degree to which a measurement correctly estimates the true value of the object being measures
first requirement of measurement
can it be repeated consistently with minimal error?
second requirement of measurement
does the test/measure actually measure what it claims to measure?
A useful clinical instrument also must be able to detect ______ over time
change
the measure must also be ____ to change
sensitive
standardized response mean (SRM)
expresses change in standard deviation units
requires numerical outcomes
=(mean of pre to post test change) / (stdev of change score)
.8 = large change
