Chapter 10: Introduction to Simple Experiments Flashcards
Experiment
- Specifically means that the researchers manipulated at least one variable and measured another
- It can take place in a laboratory and just about anywhere else - anywhere a researcher can manipulate one variable and measure another
Manipulated Variable
A variable that is controlled, such as when the researchers assign participants to a particular level (value) of the variable
- Independent variable
Measured Variable
- Take the from of records of behavior or attitudes, such as self - reports, behavioral observations, or psychological measures
- The researchers simply record what happens
- Dependent variable
Conditions
Levels of an indepedent variable (and it should not be confused with it’s levels)
Control Variable
- Any variable that an experimenter holds constant
- Want to make sure all participants are identical except the variable that is being manipulated
- Also called the nuisance variable
Comparison Group
(comparison condition)
- If the independent varibales did not vary, a study should not establish covariance
Treatment Group(s)
(one or more treatment conditions)
- Give variables on each side such as doeses of medication
Control Group
(no treatment condition)
- It is a level of an independnt variable that is intended to represent “no treatment” or a neutral condition
Placebo Group
(placebo control group; appears to the participants to be an active treatment, but does not actually contain the active treatment)
- When the control group is exposed to a treatment such as sugar
Experiments Establish Temporal Precedence
- Where the cause variable precedes the effect variable
- The ability to establish temporal precedence, by controlling which variables come first, is a strong advantage of experimental designs
- The ability to establish temporal precedence is a feature that makes experiments superior to correlational designs
Confound
- Or potential threats to internal validity
- Can mean confuse
- When a study has a confound, you are confused about what is causing the change in the dependent variable
Design Confound
- Is an experimenters mistake in designing the independent variable
- Is a classic threat to internal validity
- When a experiment has a design confound, it has poor internal validity and cannot support a causal claim
Systematic Varibality
- Don’t want another variable making a change
- It’s a problem
- It is important to reduce systematic variability through proper experimental design and control
Unsystematic Variability
- Less of a problem
- Change that is not consistent
- It is somewhat random
Selection Effect
- When participants in one level is systematic different than the other participants conditions
- When the experimenters let participants choosle (select) which group they want to be in
- May result if the experimenters assign one type of person to one condition, and another type of person to another condition
Random Assignment
- Avoids selection effect
- Random assignment is where every participants have an equal chance of any conditions
- Well-designed experiments often use random assignment to avoid selection effects
- Is a way of systematizing the types of participants who end up in each level of the independent variable
Independent Group Design
(aka between sibjects design or between groups design)
- When participanst are exposed to just one level of condition
Matched Groups
- Avoiding selection effects
- Has the advantage of randomness
- Requires more time and often more resources than random assignment
Within Group Design
(aka within - subjects design)
- Each particpansts are exposed to all levels of conditions
Posttest - Only Design
- Participants are randomly assigned to each level and are tested on the dependent variable once
- Also known as as an equivalent groups
Within - Groups Designs
Participants are exposed to all conditions (levels)
Repeated - Measures Design
Is a type of within - groups design in which participants are measured on a dependent variable more than once, after exposure to each level of the independent variable
Concurrent - Measures Design
Which is when all conditions are exposed roughly at the same time and a single attitudinal or behavioral preference is the dependent variable
Advanatages of Within - Groups Designs
- Participants in your groups are equivalent because they are the same participants and sevres as their own controls
- These designs give researchers more power to notice differences between conditions
- Within - groups designs require fewer participants than other designs