Chap 5: True Experiments, Single-Factor Design

Question 1

What are true experiments?

Answer 1

Experiments where the experimenter has complete control over the experiment.

Question 2

What are quasi experiments?

Answer 2

Experiments where the experimenter lacks a degree of control over the conditions that is possible in a true experiment.

Question 3

How do the differences in a true and quasi experiment affect the determination of causality?

Answer 3

As there is more control in a true experiment, it allows the inference of causality with more certainty compared to a quasi experiment.

Question 4

What are factors?

Answer 4

Independent variables of an experiment.

Question 5

What are levels?

Answer 5

The particular value of an IV or factor.

For example, in an experiment on how running affects mood. There would be 2 levels in the IV: running and no running.

Question 6

What are conditions or treatments?

Answer 6

Refers to a particular way in which subjects are treated based on the IV.

Question 7

Decide whether the following research questions could be studied using a true experimental research design:

1. Effect of monetary incentive to take an intelligence test on actual test performance.
2. Effect of age-related cognitive decline on emotional regulation skills.
3. Effect of a group-based exercise program on mobility and psychological well-being.
4. Effect of parietal lobe damage on arithmetic ability.

Answer 7

1. Yes
2. No
3. Yes
4. No

Question 8

What are the elements of design that are considered basics to good experimental designs?

Answer 8

Existence of a control group or control condition

Random allocation of subjects to groups

Question 9

What are carryover effects?

Answer 9

The possibility of outcome or data being influenced as a result of repeated testing.

Question 10

What are the 2 types of carryover effects?

Answer 10

Order effects and sequence effects.

Question 11

What is an order effect?

Answer 11

Changes in a subject’s performance resulting from the position in which a condition appears in an experiment.

Warm-up, learning and fatigue are examples of order effects.

Question 12

What is a sequence effect?

Answer 12

Changes in a subject’s performance resulting from interactions among the conditions themselves.

Contrast effect is an example of a sequence effect.

Question 13

What are the methods for controlling order and sequence effects in within-subjects experiment design?

Answer 13

Counterbalancing (complete/partial)

Block randomisation

Reverse counterbalancing

Question 14

What is counterbalancing?

Answer 14

Arranging that subjects experience the various conditions in different orders.

For example in 2 subjects (1 & 2) with 3 conditions (ABC):

If 1 is experiencing ABC, 2 should not also be experiencing ABC but instead a different order like ACB or BAC.

Question 15

What is block randomisation?

Answer 15

Randomising the order of conditions, with the restriction that each condition is presented once before any condition is repeated.

For example, there are 4 conditions ABCD, block randomisation might give the following sequence: BCAD, ADCB instead of AABD, BCCD.

Question 16

What is the difference between complete counterbalancing and partial counterbalancing?

Answer 16

Complete counterbalancing is when there is random assignment to all possible sequences.

Partial counterbalancing is when instead of every possible sequence, each condition occurs in every rank order. A latin square is an example of partial counterbalancing.

For example: If there are 3 conditions, ABC.

Full counterbalancing would be: ABC, ACB, BAC, BCA, CAB, CBA

Partial counterbalancing would be: ABC, BAC, CBA

Question 17

What are some designs to avoid?

Answer 17

One-group posttest-only (Unable to determine any changes to DV were due to IV)

One-group pretest-posttest design (No control group, no certainty that the changes are due to the treatment)

Posttest-only with non-equivalent control group (Controls should be recruited BEFORE the experimental group has undergone the experimental condition, there should also be random assignment for conditions)

Question 18

What is a single-factor design experiment?

Answer 18

When the experiment has only a single IV or single factor.

Question 19

You’re investigating how different levels of noise affect concentration. You have three groups of participants. One group works in a quiet environment, the second group in a moderately noisy room, and the third group in a loud room. Afterward, all participants complete a concentration task.

How many factors and levels are there?

Answer 19

One factor (noise)

Three levels (quiet, moderately noisy, loud)

Question 20

You’re testing whether caffeine improves memory. You have two groups: one group drinks a caffeinated beverage, and the other drinks a placebo (a decaf beverage). Afterward, both groups perform a memory recall test to see how well they remember a list of words.

How many factors and levels are there?

Answer 20

One factor (caffeine)

Two levels (caffeinated beverage and decaf beverage)

Question 21

You want to investigate how background music affects task performance. Every participant completes the same task twice—once with background music and once in silence.

How many factors and levels are there?

Answer 21

One factor (background music)

Two levels (background music, silence)

Question 22

You’re looking at how age affects reaction time. You recruit young adults aged 18-25 and older adults aged 60-70. Both groups complete a reaction time task, and you compare their results.

How many factors and levels are there?

Answer 22

1 factor (age)

2 levels (young adults, 18-25 and older adults, 60-70)

Question 23

You want to find out which area of the brain is responsible for the mental rotation of asymmetrical letters, such as “P”, “F”. While participants attempt to mentally rotate the letters, you interfere with the processing in one of three specific brain areas using TMS: left parietal lobe, right parietal lobe, or a sham stimulation at the midline of the brain.

Is this a true experiment? How many factors and levels are there?

Answer 23

Yes, it is a true experiment as you are able to manipulate with the IV (brain area).

1 factor (area of the brain)

3 levels (left parietal lobe, right parietal lobe, sham simulation at midline of brain)

Question 24

You want to see if both the study method and the time of day impact test performance. You have four groups. Some participants use visual learning while others use auditory learning. Additionally, half of the participants study in the morning, and the other half study in the evening. Afterward, everyone takes the same test.

How many factors and levels are there?

Answer 24

2 factors (study method & time of day)

2 levels for study method (visual learning & auditory learning)

2 levels for time of day (morning & evening)