Threats to Internal Validity Flashcards
A second variable that unitentionally varies systematically with the independent variable
design confound
In an independent-groups design, when the two independent variable groups have systematically different kinds of participants in them
Selection effect
In a repeated-measures designs, when the effect of the independent variable is confounded with carryover from one level to the other or with practice fatigue or boredom
Order effect
An experimental group improves over time only because of natural development r spontaneous improvement
Maturation
An experimental group changes over time because of an external factor that affects all of most members of the group
History
An experimental group whose average is extremely low (or high) at pretest will get better (or worse) over time because the random events that caused the extreme pretest scores do not recur the same way at posttest
Regression to the Mean
An experimental group changes over time, but only because the most extreme cases have systematically dropped out and their scores are not included in the posttest
Attrition
A type of order effect: An experimental group changes over time because repeated testing has affected the participants. Practice effects (fatigue effects) are one subtype.
Testing
An experimental group changes over time, but only because the measurement instrument has changed.
INstrumentation
An experimental group’s ratings differ from a comparison group’s, but only because the researcher expects the groups’ ratings to differ.
Observer bias
Participants guess what the study’s purpose is and change their behavior in the expected direction.
Demand characteristic
Participants in an experimental group improve only becasue they believe in the efficacy of the therapy or drug they recieve.
Placebo effect
Ex. If people who take notes on laptops answer harder question than those who take notes long hand
Design confound
Ex. In the autism study, some parents insisted they wanted their children to be in the intensive treatment group rather than the control group
Selection effect
Ex. People rated the shared chocolate higher only because the first taste of chocolate is always more delicious than the second one.
Order effect
Ex. Disruptive boys settle down as they get used to the camp setting
Maturation
Ex. Dorm residents use less air conditioning in November than september becasue the weather is cooler.
History
Ex. A group’s average is extremely depressed at pretest, in part because some members volunteered for therapy when they were feeling much more depressed than usual
Regression to the mean
Ex. Because the most rambunctious boy in the cabin leaves camp early, his unruly behavior affects the pretest mean but not the posttest mean.
Attrtion
Ex GRE verbal scores improve only because students take the same version of the test both times and therefore are more practiced at posttest.
Testing
Ex. Coders get more lenient over time, so the same behavior is coded as less distruptive at posstest than at pretest.
INstrumentation
Ex The researcher expects a low sugar diet to decrease the campers unruly behavior, so he notices only calm behavior and ignores wild behavior.
Observer Bias
Ex. Campers guess that the low sugar diet is supposed to make them calmer, so they change their behavior accordingly
Demand Characteristic
Ex. Women receiving cognitive therapy improves simply because they believe the therapy will work for them.
Placebo Effect
Q. Did the researcher turn potential third Variables into control variables
Design Confound
Q. Did the researcher use random assignment or matched groups to equalize groups?
Selection effect
Q. Did the researchers counterbalance the orders of presentation of the levels of independent variable?
Order effect
Q. Did the researchers use a comparison group of boys who had an equal amount of time to mature but who did not receive the treatment?
Maturation
Q. Did the researchers include a comparison group that had an equal exposure to the external factor but did not receive the treatment?
History
Q. Did the researchers include a comparison group that was equally extreme at pretest but did not receive the therapy?
Regression to the mean
Q. Did the researchers compute the prestest and posttest scores with only the ifinal sample included, removing any dropout/s data from the pretest group average?
Attrtion
Q. Did the researchers have a comparison group take the same two tests? Did they use a posttest only design or did they use alternative forms of the measure for the pretest and posttest
Testing
Q. Did the researchers train coders to use the same standards when coding? are pretest and posttest measures demonstrably equivalent?
INstrumentation
Q. Were the observers of the dependent variable unaware of which condition participants were in?
Observer bias
Q. Were the participants kept unaware of the purpose of the study> Was it an independent groups design which makes participants less able to guess the study/s purpose?
Demand characteristic
Q. DId a comparison group recieve an inert drug/therpay
Placebo Effect
