Variable Manipulation
Experiments require a _______ variable and a _______ variable
Manipulated & Measured
Record of behaviors or attitudes (self-report, behavioral observation, physiological measures)
Measured variable
A group that is given no treatment, or a neutral treatment
Control group
Ed wants to determine if caffeine has any effects on student performance. Ed divides students into three groups. Group 1 has water, Group 2 has caffeinated tea, and Group 3 has coffee. All students drink at the same time, and take the quiz in the same room one hour later.
What is the manipulated variable, and what is the measured variable?
Manipulated: Caffeine level
Measured: Student performance
Luisa is studying the impact of a new treatment on patients with insomnia. She gives half of the patients Treatment A (the new treatment) and the other half Treatment B (the traditional treatment). She ensures that all patients receive a standardized dosage at the same time each day throughout the study.
How do we know this is an experiment?
There is a manipulated variable
Assign participants to different groups/levels/values
Manipulated variable
Do researchers measure the independent variable or the dependent variable?
Dependent variable
When participants are given a fake treatment that does not do anything (researchers know but participants do not)
Placebo control group
Ed wants to determine if caffeine has any effects on student performance. Ed divides students into three groups. Group 1 has water, Group 2 has caffeinated tea, and Group 3 has coffee. All students drink at the same time, and take the quiz in the same room one hour later.
What are the levels of the manipulated variable?
Water
Caffeinated tea
Coffee
Luisa is studying the impact of a new treatment on patients with insomnia. She gives half of the patients Treatment A (the new treatment) and the other half Treatment B (the traditional treatment). She ensures that all patients receive a standardized dosage at the same time each day throughout the study.
What are the comparison groups?
New Treatment (A)
Traditional Treatment (B)
Do researchers manipulate the independent variable or the dependent variable?
Independent variable
What are confounds?
Alternative explanations
Group other than the control group (receives treatment)
Treatment group
Ed wants to determine if caffeine has any effects on student performance. Ed divides students into three groups. Group 1 has water, Group 2 has caffeinated tea, and Group 3 has coffee. All students drink at the same time, and take the quiz in the same room one hour later.
Was water a control group or a placebo?
Control group
Luisa is studying the impact of a new treatment on patients with insomnia. She gives half of the patients Treatment A (the new treatment) and the other half Treatment B (the traditional treatment). She ensures that all patients receive a standardized dosage at the same time each day throughout the study.
Is there a control group and a control variable?
Control group: There is no control group because there is no group receiving no treatment
Control variable: Dosage and time of day
Levels (groups) of a variable
Conditions
An experimenter's mistake in designing the independent variable, where the independent variable systematically varies with some other variable
Design confound
A group (level) to compare with another group (level)
Comparison group
Ed wants to determine if caffeine has any effects on student performance. Ed divides students into three groups. Group 1 has water, Group 2 has caffeinated tea, and Group 3 has coffee. All students drink at the same time, and take the quiz in the same room one hour later.
What were some control variables Ed included?
When students drink
Where students take the quiz
Time between drinking and taking the quiz
Luisa is studying the impact of a new treatment on patients with insomnia. She gives half of the patients Treatment A (the new treatment) and the other half Treatment B (the traditional treatment). She ensures that all patients receive a standardized dosage at the same time each day throughout the study.
Luisa found that patients who received Treatment A slept more than those who received Treatment B. Upon investigation, she noticed that most of the patients who received treatment A were in rooms with windows facing away from the sunrise. What validity is in question and why?
Internal validity
There is a confound (an alternative explanation for the results), so she may have been measuring the effects of a variable other than Treatment.
Variables that are held constant to ensure only one variable is varying at a time (entails manipulation of a variable)
Control variables
True or False:
Confounds are one of the three major threats to internal validity
True
Why are experiments better than experience?
Experiments have comparison groups, and experiences do not
Ed wants to determine if caffeine has any effects on student performance. Ed divides students into three groups. Group 1 has water, Group 2 has caffeinated tea, and Group 3 has coffee. All students drink at the same time, and take the quiz in the same room one hour later.
Ed decides to run his experiment again, this time with Group 4, which will receive tea that students will be told is caffeinated, even though it is not. What is Ed choosing to include in this new version of the study?
Placebo
Luisa is studying the impact of a new treatment on patients with insomnia. She gives half of the patients Treatment A (the new treatment) and the other half Treatment B (the traditional treatment). She ensures that all patients receive a standardized dosage at the same time each day throughout the study.
Why should Luisa not opt to have a control group or placebo control group?
It would be unethical to withhold treatment from patients.