CHAPTER 10 True Experiments, Part 1: Single-Factor Designs

Question 1

true experiment:

Answer 1

research procedure in which the scientist has complete control over all aspects

the who, what, when, where, and how

changes in the dependent variable were caused by the independent variable

Question 2

quasi experiment:

Answer 2

research procedure which does not meet the requirements of a true experiment

Question 3

factors:

Answer 3

the independent variables of an experiment

• The independent variables of an experiment are often called the factors of the experiment

Question 4

level:

Answer 4

in an experiment, a particular value of an independent variable

• An independent variable always has at least two levels—if it didn’t, it wouldn’t be a variable. The two levels of handling in this example would be handling versus no handling. It is possible for an independent variable to have any number of levels
• often different levels represent the absence or presence of something

Question 5

condition

Answer 5

a group or treatment in an experiment (AN IV)

• the broadest of the terms used to discuss independent variables. It refers to a particular way in which subjects are treated.

Question 6

treatment:

Answer 6

another word for a condition of an experiment (AN IV)

Question 7

Subject variables represent variables of interest that cannot be

Answer 7

manipulated or to which level of the independent variable subjects cannot be randomly assigned

eg: sex, age, race

Question 8

Advantages of within subjects design

Answer 8

• Typically, within-subjects designs require fewer subjects than between-subjects designs.
• Within-subjects designs control for within group differences between levels of the independent variables because each level consists of the exact same subjects.

Question 9

When not to use within subject design

Answer 9

• When order or sequence effects cannot be controlled for through counterbalancing or other techniques

Question 10

two basic elements of good experimental design

Answer 10

• (1) the existence of a control group or a control condition and
• (2) the random allocation of subjects to groups.
• Can have 2 groups: the experimental and the control
• You’d need random assignment

Question 11

order effects:

Answer 11

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

• Order effects are more general and result from warm-up, learning, fatigue, and the like

Question 12

sequence effects:

Answer 12

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

• Sequence effects are the result of interactions among the conditions themselves.
• Let’s say you play me ambient music after I hear metal then I will find it extremely slow versus if I heard it after listening to water drop then I’d find it upbeat (my example)

Question 13

counterbalancing:

Answer 13

controlling for order and sequence effects by arranging that subjects experience the various conditions in different orders

• For example, if taste testing two juices, have half the participants taste the orange juice first and the grapefruit juice second. The other half of the participants would test the juices in the opposite order (grapefruit first, and orange second)

Question 14

Within-subject design:

Answer 14

when all participants experience all conditions

• Controlling for order and sequence effects within subjects is possible when each subject receives each condition.
• The best procedure is to randomize the order of conditions for each subject.

Question 15

block randomization:

Answer 15

control procedure in which the order of conditions is randomized but with each condition being presented once before any condition is repeated

• Block randomization is particularly useful if you want to present each condition at least twice and your experiment requires two or more sessions. So block randomization is most useful when conditions are presented several times to each subject
• Example: BCAD, ADCB is block randomization instead of AABDBCCD
• So block randomization is most useful when conditions are presented several times to each subject

Question 16

reverse counterbalancing:

Answer 16

method of control in which conditions are presented in order the first time and then in reverse order

• This technique is known as ABCCBA sequence, or ABBA for short
• Because some experiments have effects that may carry over from one condition to the next, such as task familiarity in the example above, it is important to take steps to control them. Reverse counterbalancing works well as a control technique when you suspect that the possible confounding variables will act in a linear manner over conditions

Question 17

How do you control for order and sequence effects within groups?

Answer 17

• each condition occurs an equal number of times in each rank order position and follows every other condition an equal number of times. Thus, you have controlled for order and sequence within a group of subjects, even though every subject experiences a biased sequence.

Question 18

Latin square:

Answer 18

control procedure in which each subject experiences each condition in a different order from other subjects

latin square - control for order effect in within subject: (fatigue)

• the more you get used to lifting weights the heavier they seem
• estimate the weight of a10, b12, c14, d16
• 8 subjects:
• alternate the order in which they get the weights
• a,b,c,d is one b,c,d,a then c,d,a,b then d,a,b,c is the latin square way to go

Question 19

two-conditions design:

Answer 19

simplest research design, involving only two conditions

• All subjects experience both conditions in counterbalanced order. Despite its simplicity, this design is not used as often as one might expect, for two reasons. First, many experiments involve more than two conditions. Second, there is the possibility of carryover effects from one condition to the other

Question 20

multiple-conditions design:

Answer 20

research design that involves more than two conditions

• The first reason researchers choose a multiple-conditions design is that seldom do they want to ask a simple yes or no question.
• second reason for conducting multiple-conditions experiments is to determine the shape of the function that relates the independent and dependent variables.
• A third reason for doing multiple-conditions experiments is the presence of more than one rival hypothesis that must be ruled out

Question 21

When are between-subjects designs preferred over within-subjects designs?

Answer 21

• when the possibility of large order or sequence effects is present

Question 22

Describe three designs to avoid in research, and give reasons for avoiding them.

Answer 22

one-group posttest-only design: research design that measures the behavior of a single group of subjects after they are given a treatment. And with no baseline measurement

nonequivalent control group: a group of subjects that is not randomly selected from the same population as the experimental group

one-group pretest- posttest design: research design that measures the behavior of a single group of subjects both before and after treatment