chapter 11 Flashcards
(22 cards)
what is a maturation effect
a change in behaviour that emerges more or less spontaneously over time
what are history threats
an external factor that systematically affects most members of the treatment group at the same time as the treatment itself
- something specific changed
what is a regression threat
refers to a statistical concept called regression to the mean
- when a group average is unusually extreme at time 1, it’s likely to be less extreme at time 2 - more the average
- only occur in a pretest/posttest design
- explained by fortunate or unfortunate events
what is attrition
a reduction in the pps that takes place before the research is finished
when does attrition become problematic
- when it’s systematic - only a certain type of people leave
what is a testing threat
- a specific type of order effect that refers to the change in the pps as a result of taking a test more than once
- practice effects
- to avoid - use a posttest only or different tests for the pretest and posttest
what is an instrument threat
occurs when a measuring instrument changes over time
- observers changing standards over time
what is a selection history effect
an outside event or factor affects only those at one level of the independent variable
what is selection attrition effect
only one group experiences attrition
what is observer bias
occurs when researchers expectations influence their interpretation of the results
- effects internal validity and construct validity
how can researchers avoid observer bias and demand characteristics
- double bind study
- masked design
what is a masked design
pps know what group they’re in but the researchers don’t
what is a placebo effect
occurs when people receive a treatment and really improve but only because they believe they are receiving a valid treatment
what is a null effect
the independent variable does not have an influence on the dependent variable and it occurs quite frequently
what can cause not enough difference between groups
- weak manipulations
- insensitive measures
- ceiling and floor effects
what is a ceiling effect
all the scores are squeezed together at the high end
what is the floor effect
all the scores cluster together at the low end
how can you detect weak manipulations, ceilings and floors
a manipulation check
what is noise/error variance
when there is too much unsystematic variability within each group
- a difference might not be detected
- the more variability, the more 2 groups overlap with each other
what is a measurement error
a human or instrument factor that can randomly inflate or deflate a persons true score on the dependent variable
- the more sources of random error, the more variability
what is situation noise
external distractions
what is power
an aspect of statistical validity, it is the likelihood that a study will return an accurate result when the independent variable really has an effect
