week 4 Flashcards
define independent variable
in an experimental design (EXP) the independent variable is manipulated by the researcher and consists of two or more treatment conditions.
aka as a predictor variable in non-experimental designs or correlational research.
this is the variable that goes on the x-axis on a graph.
this is the variable related to changes that we see in our dependent variable → Independent variables predict the outcome (dependent variable).
predictor variable helps to predict an outcome.
define dependent variable
in an experimental design uses dependent variables (vocab term)
non-experimental or correlational research uses outcome variable. (vocab term)
dependent is very similar to outcome.
The dependent variable or the outcome variable is the variable that’s observed to see changes to assess the effects of either manipulation of the independent variable or naturally occurring changes in value of the predictor variable.
will predict changes in your outcome
define extraneous variable
This is a variable that’s not your predictor.
And it’s not your outcome.
It’s anything else, any other factor involved in a study.
what are the defining characteristics of a between-subject design
between subjects is used in an experimental design where the researcher manipulates an independent variable
in a between-subjects design, we’re comparing scores from different groups of individuals,
groups of individuals all made up of different people.
is used to determine whether differences exist between two or more treatment conditions
Therefore, scores are considered independent, because scores are provided by separate, unique participants.
what are the defining characteristics of a within-subject design
within-subjects designs compare scores in two or more different treatment conditions by observing or measuring that behavior in the same individual who participates in each condition.
the same individual is going to be in all of the treatment conditions.
looking for differences between treatment conditions by looking at the changes within the same person or group of people.
actually comparing one individual to their other score
rather than looking at the group average, which we do in between-subjects designs.
each individual in the study has to have more than one score if it’s to be a pure within-subjects design.
explain how INDIVIDUAL DIFFERENCES in BETWEEN-SUBJECTS DESIGN threaten internal validity
the primary disadvantage of a between-group design is each score is obtained from a unique individual who has personal characteristics that are different from all other participants
individual difference are personal characteristics that can differ from one participant to another
assignment bias - individual differences can become confounding variables like one group is remarkably older or more severe impairments producing high variability of the score threatening internal validity
confounding from environmental variables
explain how DIFFERENTIAL ATTRITION in BETWEEN-SUBJECTS DESIGN threaten internal validity
big differences in attrition rates between control and comparison groups can threaten internal validity because we don’t know whether the obtained differences between treatment conditions are caused by the treatments or by differential attrition
explain how COMMUNICATION BETWEEN GROUPS in BETWEEN-SUBJECTS DESIGN threaten internal validity
diffusion refers to the spread of the treatment (in this case participants sharing info between groups) from the experimental group to the control group which tends to reduce the difference between the two conditions
what are the 3 primary techniques for limiting confounding variables by individual differences in between-subjects experiments
holding a participant variable constant like age or gender
random assignment
matching across groups
explain the general advantages and disadvantages of a within-subjects design
advantages:
requires fewer participants than between-subjects
eliminates or reduces problems based on individual differences being a confound, because each individual is going to be in all the treatment conditions
disadvantages:
participants’ performance can be susceptible to time-related factors, which can threaten internal validity. like fatigue effects and practice effects
participants attrition
describe how factors such as testing effects, history, maturation and instrumentation as well as statistical regression can threaten the internal validity of a within-subjects design
History, maturation, all of these different testing effects, and statistical regression to the mean are all factors that can affect one’s true score and one’s score and measurement when they’re participating in within-subjects designs.
maturation is when a group of individuals is being tested in a series of treatment conditions and any physio or pyscho changes occurs in participants during the study may influence the score
instrumentation refers to changes in the measuring instrument that occurs over time
statistical regression refers to the tendency for extreme scores on any measurement to move towards the mean (regress) when the measurement procedure is repeated - individual who score high on the first test are likely to score lower on second testing, vice versa
what are the 3 measures of central tendency
mean, median and mode
what are the two measures of variability
Standard deviation
X axis - the spread of score is a representation of the variation/standard deviation in your sample on a bell shaped curve
is the square root of the variance
Most frequently used
interpreted in the same units of measure as the mean.
easier to interpret because of that.
standard deviation = SD
Variance
is a measure of variability
this is the average squared distance of scores from the mean.
when we compute variance– putting it simply, what we’re looking at is the distance between each person’s score from the average.
hard to interpret because we’re actually squaring units so that why standard deviation is more oftenly used
it’s a measure of how far each person scored from the average
define mean
mean or the average
Middle of bell shaped curve
mean = M that’s italicized. And median is MDN italicized
explain how the purpose of descriptive research design differs from the purposes of experimental/non-experimental research designs
descriptive: describes what’s naturally occurring
not looking at a relationship btwn variables but rather variables themselves
experimental/nonexperimental: has manipulated variables
interested in cause and effect relationship between variables
