exam #2 Flashcards
How do studies using the experimental research strategy differ from other types of research?
Only experiments can demonstrate a cause-and-effect relationship between variables.
Dr. Jones is interested in studying how indoor lighting can influence people’s moods during the winter. A sample of 100 households is selected. Fifty of the homes are randomly assigned to the bright-light condition where Dr. Jones replaces all the lights with 100-watt bulbs. In the other 50 houses, all the lights are changed to 60-watt bulbs. After two months, Dr. Jones measures the level of depression for the people living in the houses. In this example, how many dependent variables are there?
1
Research indicates the people who suffer from depression also tend to experience insomnia. However, it is unclear whether the depression causes insomnia or the lack of sleep causes depression. What problem is demonstrated by this example?
the directionality problem
In an experiment, what is the purpose for manipulating the independent variable?
It helps establish the direction of the relationship and it helps eliminate the third-variable problem.
In order to establish an unambiguous relationship between two variables, it is necessary to eliminate the possible influence of which of the following variables?
Confounding variables
Which of the following characteristics are necessary for an extraneous variable to become a confounding variable?
It must change systematically when the independent variable is changed.
In an experiment comparing two treatments, the researcher assigns participants to treatment conditions so that each condition has fifteen 7-year-old children and ten 8-year-old children. For this study, what method is being used to control participant age?
Matching
Holding a variable constant is a technique for removing one threat to ________, but it can limit the ________ of an experiment.
internal validity, external validity
Which of the following is the primary goal for randomly assigning participants to treatment conditions in an experiment?
Minimize the likelihood that a participant variable (such as age or gender) becomes a confounding variable
What is the purpose for using a control condition in an experiment?
It provides a baseline that can be used to evaluate the size of the treatment effect.
An experiment includes a treatment condition, a no-treatment control, and a placebo control. Which two conditions should be compared to determine the size of the effect that is actually caused by the treatment?
Placebo versus treatment
A researcher exposes people to a stressful situation (such as public speaking) to examine the effect of stress on depressed mood. Why would the researcher also include a measure of stress?
It is a manipulation check.
A researcher moves an experiment out of the laboratory and into the real world. This type of research is called
a field study.
Researchers often use simulation experiments in an attempt to obtain the _________ of an experiment and still keep much of the _________ of research conducted in the real world.
internal validity, external validity
Although field studies tend to have higher external validity than traditional laboratory studies, what risk do they tend to have?
Lower internal validity
Which statement best characterizes a between-subjects experimental design?
Each participant is assigned to one condition of the experiment.
Which of the following accurately describes the scores in a between-subjects experiment?
Only one score is obtained for each participant.
If a between-subjects experiment produces 50 scores in treatment 1 and 50 scores in treatment 2, then how many participants were in the entire experiment?
100 participants
In a between-subjects experiment, if the participants in one group have characteristics that are different from the participants in another group, then which of the following is threatened?
Internal validity
For a between-subjects experiment, which of the following is a possible threat to internal validity?
Individual differences that exist between treatments
Which of the following does not guarantee that a specific participant variable will not become a confounding variable?
Randomizing the variable across treatment
Which of the following is a limitation of using matching rather than random assignment to form groups in a between-subjects experiment?
Matching requires another measurement procedure.
How does holding a variable constant prevent the variable from becoming a confound?
It eliminates the possibility that the variable will be substantially different from one group to another.
variance
a statistical value that measures the size of the differences from one score to another
Whenever there are large differences between ___, there is large ___.
individuals; variance
true or false: with between subjects design we want to minimize variance within treatments
true
what is it best way to minimize the negative consequences of high variance?
- standardize treatments
- minimize individual differences between the participants
what happens when you minimize individual differences?
you lessen external validity
Which of the following maximizes the likelihood of a successful research result?
Increase the differences between treatments and decrease the variance within treatments
Which of the following is an option for limiting the variance within treatment conditions?
Hold a participant variable constant
Which of the following is a potential problem with holding a participant variable constant?
It threatens the external validity of the study.
define: differential attrition
refers to differences in attrition rates from one group to another and can threaten the internal validity of a between-subjects experiment
define: compensatory rivalry
the untreated group works extra hard to show that they can perform just as well as the individuals receiving the special treatment
define: resentful demoralization
the participants in an untreated group simply give up when they learn that another group is receiving special treatment
how to ensure internal validity in between subjects designs?
do not let the two groups communicate with each other
Which of the following accurately defines compensatory equalization?
One group demands the same benefits received by another group.
Which of the following accurately defines compensatory rivalry?
One group works extra hard to make up for not receiving the benefits received by another group.
Which of the following accurately defines diffusion?
Elements of the treatment in one group have spread to another group.
define: two group design
The researcher manipulates one independent variable with only two levels
what is the primary disadvantage of two group design?
provides little information
Which of the following is the primary limitation of a two-group design?
It may not provide a complete picture of the relationship between the variables.
When comparing means in a two-group design, which statistical analysis is most appropriate?
Independent-measures t-test
When comparing means in a single-factor multiple group design, which statistical analysis is most appropriate?
Single-factor ANOVA
How many participants would be needed for a within-subjects experiment comparing four different treatment conditions with a total of 20 scores in each treatment?
20
In a within-subjects research study comparing different treatment conditions at different times, what kind of validity is threatened by factors that change over time, such as history and maturation?
Internal validity
In a within-subjects study that extends over a relatively long time, it is possible that there will be systematic changes in the participants’ skills or knowledge during the time of the study. If these changes influence the participants’ scores, causing scores at the end of the study to be different from scores at the beginning, then what is the effect is called?
Maturation
what is the result of counterbalancing?
to distribute the order effects evenly between the two treatments; that is, the order effects are balanced across the treatment conditions
what are some limitations of counterbalancing?
- does not eliminate order effects
What is the effect of increasing the time between treatment conditions in a within-subjects experiment?
It decreases the threat of time-related history effect.
For a within-subjects study comparing two treatments, A and B, a researcher expects that practice in the first treatment will improve the participants’ scores in the second treatment. If the order of treatments is counterbalanced, then what scores will be influenced by the practice?
Scores in treatment A for half the participants and scores in treatment B for half the participants.
Which of the following describes a completely counterbalanced within-subjects experiment?
A series of treatments is presented in every possible sequence.
advantages of within subjects designs
- requires fewer participants
- eliminates problems with individual differences
- more likely to detect a treatment effect
disadvantages of within subjects designs
- each participant often goes through a series of treatment conditions, with each treatment administered at a different time
- participant attrition
define: matched subjects design
uses a separate group for each treatment condition, but each individual in one group is matched one-to-one with an individual in every other group
What is measured and removed to reduce the variance in within-subjects design compared to a between-subjects design.
The individual differences
Which of the following is an advantage of the between-subjects design versus the within-subjects design?
It eliminates the risk of order effects.
For an experiment that compares two treatment conditions with ten scores in each treatment, which design would require fewer subjects?
Within-subjects design
What is the appropriate hypothesis test for a within-subjects design comparing mean differences for three treatment conditions?
A repeated-measures analysis of variance.
Which of the following is an advantage of a two-treatment within-subjects design compared to a multiple-treatment design?
- There is a reduced risk of participant attrition.
- There is a reduced risk that time-related factors influence the data.
- It is easier to counterbalance a design with only two treatments.
what is the key to experimental research?
random assignment - people in the sample are randomly assigned to the different conditions in your study/being exposed to the different levels of your independent variable
what are the 4 basic elements of experimental research?
- manipulation
- measurement
- comparison
- control
define: directionality problem
occurs when there is an association between two variables, but it is not possible to determine which variable is the one that causes changes in the other variable (is it variable a that is affecting variable b or the other way around?)
define: third variable problem
occurs when there is an association between two variables, but changes in one variable do not directly cause changes in the other variable; instead they are both influenced by a third variable that causes them both to vary together - aka confounding variable
true or false: correlation = causation
false
define: extraneous variable
any other variable that are not the independent or dependent variable (ex: gender, colour of the walls, amount of light) - however, not all of these things are able to impact the dependent variable - not possible to control all of them in a study but hone in on the most influential ones
define: confounding variable
an extraneous variable (usually unmonitored) that changes systematically along with the variables whose association is being studied, and provides an alternative explanation for the observed results
what are 3 potential confounding variables in experimental research?
- environment variables
- participant variables
- time related variables
what are 3 methods of control for experimental research?
- random assignment
- holding the variable constant
- matching
define: experimental group
the group of participants who receive treatment/intervention
define: control group
the group of participants who do not receive any treatment or intervention
define: manipulation check
checking to make sure that there actually is a difference between the two conditions
how can mean scores on the DV be compared?
a t-test or an anova test
what does a small p value for the statistical test mean
there is a small chance that the difference between means was a fluke, and that there is a good chance that we would find about the same difference between means if we did the study again with a new sample of participants
what does a p value less than 0.5 mean
often used to indicate statistical significance
what must the comparison groups be for between subjects designs?
- treated equally
- created equally
- composed of equivalent indiviuals
define: assignment bias
occurs when the two groups are different on some characteristic
what is an important confounding variable for within subjects designs
time related - they have to be done at different times because the same people are used for both groups
what are some threats to internal validity for within subjects designs?
- history - personal circumstances
- maturation - physiological and psychological changes
- order effects - behaviour is affected from previous procedure
- instrumentation - measurement procedures change throughout the experiment
- regression toward the mean - first procedure is extreme, scores level out on the second one
define: counterbalancing
Participants are exposed to the different study conditions (levels of the IV) in different orders so that they conditions are matched with respect to time
complete counterbalancing
Means that at least one participant gets exposed to all the conditions (levels of the IV) in each possible sequence of conditions
define: partial counterbalancing
involves using a few different orders of conditions rather than every possible order
what is used for partial counterbalancing?
a latin square - puts the last condition from the first sequence first in the next sequence (ABCD, DABC), each condition appears once in the sequence
