EXAM 2 Flashcards
(49 cards)
Quasi-experimental designs
No true IV
Looks like an experimental variable but
Can’t be randomly assigned
Can’t be interpreted as causing changes in the DV or outcome variable
ex– Studying the impact of a new traffic safety law by comparing accident rates before and after the law’s implementation
Extraneous variables
Variable environmental conditions over the course of the study
Individual differences among participants
Fluctuations in the physical/mental state of an individual participant
Confounding variables
an extraneous variable that covaries with your IV
It provides an alternative explanation for your findings
Threat to the internal validity of your study
Between-subjects design
Different participants are assigned to each group or condition.
Each group is exposed to a different level of the independent variable, allowing for comparisons between groups.
Random assignment/ Randomized designs
Comparing the test scores of two different groups of students, one that received the tutoring program and another that did not, to determine if the tutoring had a significant impact on math skills.
Within-subjects design
Same participants in all conditions
Repeated testing of individuals
Factor
independent variable
IV takes on different values called
Levels
Conditions
Groups
Treatments
Single factor
manipulating one independent variable with more than two levels or conditions to observe its impact on a dependent variable
ex– Experiment: Testing the Effect of Fertilizer Types on Plant Growth
Independent Variable (Single Factor):
Three different types of fertilizers:
Fertilizer A
Fertilizer B
Fertilizer C
Two group design
Simplest design
1 IV with two levels/groups
Multigroup design
1 IV with 3+ groups
Power to detect nonlinear relationships
Ex– caffeine consumption and speed of encoding
Randomizes
Random assignment to hopefully make groups equivalent on extraneous variables
Relies on chance– not guarantee that groups will be equivalent
Matched
Matched Design: Ensures groups are equal on matched characteristics.
Matched-Pairs: 2 conditions, 2 participants per match
Matched Multi-Group: 3+ conditions, 1 participant per match.
If no match, no study participation.
Solution for matched groups design
Recruit a sample of participants
Measure the participants on the extraneous variable you want to control
Group participants who scored the same (or close) on the matching variable
Randomly assign participants in the match-groups to each of the conditions
Matching vs. random assignment
Matching– guarantee
Random assignment– chance
The more participants you have, the more likely it is that random assignment will be successful
Within subjects design
The same participants are used in all conditions
Logic is similar to the matched-groups design
Threats to validity
Purpose is to control individual difference extraneous variables
ex– testing the same group of students’ math skills before and after a tutoring program to see if there is an improvement in their scores.
Does a pre-test lead to a post-test within subject-design
No
Pre test and post test are not levels of IV
pre test is a baseline and post test assesses the effects after the experiment
Disadvantages for within subjects design
More demanding on participants
Especially if your IV has a lot of levels
Drop-out
Participants failing to complete the study
Carryover effects
Exposure to one condition affects performance in a subsequent condition
Testing affects
Performance changes over time, unrelated to IV
Sources of carryover
Learning, contrast, habituation, dishabituation, sensitization
Learning
Participants don’t just unlearn what you’ve taught them in a previous condition
Contrast
Participants may compare treatments, affecting behavior
Habituation
Repeated exposure to a stimulus that may decrease responsiveness to that stimulus
ex– traffic noise outside of your apartment becoming very unnoticeable because you are so used to it
Dishabituation
when an organism responds to a previously familiar stimulus as if it were new again.
ex– background music: you get used to it but you would notice if it stopped or changed in a noticeable way
Sensitization
when a person or organism becomes more responsive or reactive to a stimulus after being exposed to it, often due to a previous intense or disturbing experience
Testing affects
Fatigue– Participating in repeated trials can result in poorer performance in later conditions
Exhaustion, frustration, boredom, etc
Practice– Participating in repeated trials can result in better performance in later conditions
Attrition
random dropout
Ex– people move away from area
Unrelated to the topic of study
