PSC 41 UNIT 3 (PSYCHOLOGY) QUESTIONS AND ANSWERS
ELABORATIONS!!
Questions to ask when assessing internal validity
Answers :Has the researcher isolated the effect of the IV on the DV
Are the groups/experiences equal
Were all potential confounds eliminated+alternative explanations ruled out
What are the 3 essential elements that define experiments and allow for the
elimination of alternative explanations?
Answers :Start with = groups
Manipulate one variable
Observe any effect on the outcome variable
How do you create = groups?
Answers :With large number of participants: random assignment
With small number of participants: matching procedure
What is random assignment and why is it important?
Answers :Occurs after participants have been selected. All participants have =
likelihood of being placed in each treatment group.
It spreads out individual diff. so on avg. all groups should be =
How do you perform a matching procedure and why is it important
Answers :Measure the potential confounding difference, pair similar participants
together by that trait, one member of each pair assigned to each treatment
Important so that confounding difference is evenly spread across groups
, Define random sampling
Answers :Every member of the population has = likelihood of being selected into
the sample
What is the difference between random sampling and random assignment?
Answers :Sampling: Before the experiment + important for external validity
Assignment: During the experiment + important for internal validity
What are extraneous variables? When are they are a concern vs when are they not?
Answers :Variable that are not related to the treatment but can influence the
outcome (uncontrolled, not of interest to researchers)
If affecting both groups ok
If affecting only one then it may be a confounding variable
What is a confounding variable? Why is it an issue
Answers :Variables that affect one group differently from the other group; changes
at the same time as the IV;
Its effects can not be separated from effects of the IV --> alternative explanation
for change in DV
What are the 5 common threats to internal validity? When are they an issue
Answers :Selection effect
Maturation effect
Testing effect
Mortality effect (Attrition)
History effect
ELABORATIONS!!
Questions to ask when assessing internal validity
Answers :Has the researcher isolated the effect of the IV on the DV
Are the groups/experiences equal
Were all potential confounds eliminated+alternative explanations ruled out
What are the 3 essential elements that define experiments and allow for the
elimination of alternative explanations?
Answers :Start with = groups
Manipulate one variable
Observe any effect on the outcome variable
How do you create = groups?
Answers :With large number of participants: random assignment
With small number of participants: matching procedure
What is random assignment and why is it important?
Answers :Occurs after participants have been selected. All participants have =
likelihood of being placed in each treatment group.
It spreads out individual diff. so on avg. all groups should be =
How do you perform a matching procedure and why is it important
Answers :Measure the potential confounding difference, pair similar participants
together by that trait, one member of each pair assigned to each treatment
Important so that confounding difference is evenly spread across groups
, Define random sampling
Answers :Every member of the population has = likelihood of being selected into
the sample
What is the difference between random sampling and random assignment?
Answers :Sampling: Before the experiment + important for external validity
Assignment: During the experiment + important for internal validity
What are extraneous variables? When are they are a concern vs when are they not?
Answers :Variable that are not related to the treatment but can influence the
outcome (uncontrolled, not of interest to researchers)
If affecting both groups ok
If affecting only one then it may be a confounding variable
What is a confounding variable? Why is it an issue
Answers :Variables that affect one group differently from the other group; changes
at the same time as the IV;
Its effects can not be separated from effects of the IV --> alternative explanation
for change in DV
What are the 5 common threats to internal validity? When are they an issue
Answers :Selection effect
Maturation effect
Testing effect
Mortality effect (Attrition)
History effect
