Experimental Design
Dr. Bosco Is conducting a study on Treats and purring in cats. He Randomly assigns a sample of cats into two groups. One group Receives treats and the other does not. Which kind of experimental design is Dr. Bosco using?
Between/independent groups design
True or False: Only experiments can establish FULL causality
TRUE!
True or False: A design confound is the experimenters mistake in designing the dependent variable
FALSE
At least how many levels of an independent variable are needed for an experiement?
2
Explain the difference between random assignment and random sampling/selection
Random assignment - All participants have an equal chance of being assigned to conditions within an experiment.
Random sampling - All members of a population have an equal chance of being included in a sample
Dr. Miguel is interested in silly string and trouble making behavior. He sets out cans of silly string for a group of elementary school students during recess. He observes trouble making behaviors during this 30 minute period. The next day, he observes the same group of students, but does not set out any cans on silly string. Which type of design is Dr. Miguel using?
Within-groups design
By ensuring that a "cause" comes before an "effect", which criteria of causality do experimental designs help to establish?
Temporal Precedence
True or False: Variability is only a problem for internal validity if it is systematic
TRUE!
What type of variable is being described?: Dividing notetaking into two levels; Handwritten and typing, and randomly assigning participants to each level.
Independent/manipulated variable
Explain post-test only and pretest/post-test designs. How are they similar? How are they different?
The are both Between groups designs
PTO- Participants are only measured on the DV once
PT/PT - Participants are measured on the DV twice - before and after IV
Dr. Ve is conducting a study on attractiveness and group membership. She has a group of KSU students sit in an auditorium and listen to two brief speech's. One speech giver is wearing a KSU t-shirt, and the other is wearing an LSU t-shirt. After participants listen to both speech's, they are asked to rank the attractiveness of each speech giver. Which type of design is Dr. Ve using?
Concurrent-measures design
Using random assignment helps to establish which criteria of causality?
Internal validity
What are two ways to avoid selection effects?
Random assignment and matched groups
Which type of variable is being described?: Having participants take a test after being exposed to levels of the manipulated variable.
Dependent/measured variable
Explain concurrent-measure and repeated-measure designs. How are they similar? How are they different?
They are both types of within groups designs.
1. RMD - Participants are exposed to different levels of the IV at different times after measurement
2. CMD - Participants are exposed to all levels of the IV at roughly the same time
Dr. Nevs is doing an experiment on shoes and walking distance. He has all participants put on a pair of uncomfortable walking shoes, and then measures how far they walk. He then has the same group put on a pair of comfortable walking shoes, and again measures how far they walk. Which type of design is Dr. Nevs using?
Repeated-measures design
Using a comparison group helps to establish which criteria of causality?
Covariance
Dr. Kitty is designing the independent variable of her experiment on motivation in babies. She decides to divide her independent variable into an effort condition (where babies will watch the experimenter put forth effort while completing a task) and a no effort condition (where experimenters put forth no effort while completing the task). She makes the mistake of having all the naturally cheerful researchers in the effort condition and all the naturally uncheerful researchers in the no effort condition. Why is this mistake a design confound?
Systematic variability - Babies may actually be responding to cheerfulness and not effort
Which type of variable is being described?: In an experiment on note taking style, participants in both conditions watch the SAME video lecture.
Control Variable
Explain counterbalancing. What are the two types (explain)? What does this method help to rule out?
1. Presenting levels of the IV in different sequences
2. Partial counterbalancing - Either randomizing the order of IV for each participant or ensuring the IV appears in each position at least once (Latin Square)
Full counterbalancing - All possible order of conditions are presented
3. Order effects
Dr. Marcy is interested in studying the effect of quality of conversation on self efficacy. She randomly assigns participants into either a good conversation group or a poor conversation group where they have a conversation with a confederate. After participants are finished having conversations with the confederate, she has then complete a survey on self efficacy. Which type of design is Dr. Marcy using?
Post-test only design
What are the three criteria needed to establish causality?
Covariance, temporal precedence, and internal validity
Dr. Ve is analyzing the effectiveness of a motivation training program on GPA. She gets lazy and decides not to randomly assign participants to the motivation training condition and the non training condition. To make things super easy, she just puts all the participants who arrived before 9am in the motivation condition. Which design confound could affect Dr. Ve's results?
Selection effects
Identify the Independent (& its levels), dependent, and control variable(s) in the following scenario.
Dr. Bosco is studying laundry detergent and sleep quality. He has one group of participants sleep with a blanket that has been washed using Tide, and the other group sleeps with a blanket washed using Gain. He has all participants sleep with the same blanket that he purchased from target. After sleeping with the blanket, he has all participants complete a survey on sleep quality.
IV: Detergent (Gain and Tide)
DV: Sleep quality (survey)
CV: The blanket
What is the difference between independent (between) and dependent (within) group designs. Use the word "levels" in your answer.
In WGD, all participants are exposed to all levels of the IV. In BGD, different groups of participants are exposed to different levels of IV.