Task 8

Question 1

What is error variance?

Answer 1

All the variance in the dependent variable caused by factors other than the independent variable

extraneous or subject related variables such as age, gender and personality

Example: Comparison of 2 depression treatments. Other influential factors could be: family support, age, diet, season, time of day, life events, personality traits…etc

Question 2

How can you reduce error variance?

Answer 2

• by holding extraneous variables as constant as possible (e.g. experimental protocol)
• by matching subjects on influential characteristics (see Matched-Group or Within-Group design)

Question 3

Name 3 other tragedies to reduce error variance

Answer 3

1. choosing appropriate levels for the independent variable (Pilot-study)
2. Random assignment of subjects
3. Statistical analysis to determine the probability that error variance alone could cause differences between groups

Question 4

Name 3 cases of confounding and their solutions

Answer 4

• biased sample =select random sample
• biased experimenter =blind study
• extraneous variable (which changes with independent variable) = careful planning of how confounding could play a role

Question 5

Name 4 types of Between-Subject Designs

Answer 5

1. Randomized Two-Group Design
2. Randomized Multigroup Design
3. Matched-Groups Design
4. Matched-Pair Design

Question 6

How does a randomized two-group-design looks like?

Answer 6

1. you have a sample, random assignment
2. -Group A gets Treatment 1
   - Group B gets Treatment 2
3. you get a mean for each treatment (mean1 & mean2)

Question 7

Name 4 Pros and 2 Con for the randomized Two-Group Design

Answer 7

\+ requires few participants 
\+ no need for categorization 
\+ no need for pretesting
\+ simple statistical analysis 
-no Information about type of relationship
-limited sensitivity

Question 8

What is a randomized Multigroup Design?

Answer 8

All most the same like a Two-group Design, with the difference that you have the opportunity to add groups, so you can add Treatments as well

Question 9

Name 2 possibilities to add a group

Answer 9

1. Quantitative change of the independent variable (Parametic Design) e.g. Cups of coffee 1,2, or 4
2. Qualitative change of independent variable (Nonparametric Design)
   e. g. Cups of coffee 1, 2 or tea

Question 10

What is a Matched-Groups Design?

Answer 10

you have matched pairs which you split and randomly assign into Group A and Group B

Question 11

Name 3 pros and 2 cons of Matched-groups Design

Answer 11

+matching characteristic is meaningful:
+ individual differences controlled for - higher sensitivity (less error variance)
+fewer subjects needed to show effect

• matching characteristic is not meaningful:
• power of statistical test is lower compared to completely randomized

Question 12

Name 2 pros and 1 con for Matched-pair designs

What is it?

Answer 12

Matching into two groups

+ requires few participants
+ simple statistical analysis

• no information about type of relationship

Question 13

What is a Matched Multigroup Design?

1 pro 1 con

Answer 13

is matched into several groups

can give information about the type of relationship

Problem: if there are more than 3 groups a within-subject design might be better

Question 14

Explain what a within-subject design is

Answer 14

• Each subject undergoes all conditions
• No random assignment
• Also called “repeated-measures” design

Question 15

What are the pros and cons of a within-subject design 3+ und 2-

Answer 15

\+ individual differences problem solved 
\+ very powerful
\+ few participants 
- more demanding on subject 
- carryover effects 
- progressive error- general experience

Question 16

name 6 sources of carryover

Answer 16

1. learning: performance on task improves simply by repetition
2. fatigue: performance on repeated task worsens, because of fatigue (Ermüdung)
3. habituation: repeated exposure leads to reduced responsiveness (e.g. to stimulus)
4. Sensitization: repeated exposure leads to heightened responsiveness
5. Contrast: comparison of elements within the experiments can change their individual evaluation
6. Adaption: a period of adaption can either increase or decrease responsiveness

Question 17

there are 3 ways to deal with carryover effects, which are this?

Answer 17

1. Counterbalancing
2. Minimizing Carryover
3. Statistical design

Question 18

What are you doing by complete counterbalancing?

Answer 18

subjects are distributed over all different
sequencing options (eg ABC, ACB,BAC..etc)
N! if you have 4 conditions 4!

Question 19

What are you doing by partial counterbalancing?

Answer 19

a random group of possible treatment orders is selected

Question 20

what are you doing by Latin square?

Answer 20

each treatment is on each position equally often

as many options are chosen as there are treatments

Question 21

Which 2 problems do you have by dealing with carryover effects?

Answer 21

Differential carryover effects: treatments have differently strong carry over effects

Irreversible changes: lasting improvement or damage

Question 22

How can you minimize carryover?

name 2 ways

Answer 22

• Practice sessions: to eliminate carryover effects like Irreversible changes, Habituation or Sensitization
• Breaks: reducing short lasting Habituation effects, Adaptation or Fatigue

Question 23

Which statistical design can you use to deal with carryover effects?

Answer 23

Factorial Design: treats treatment order as an independent variable
• Allows for accurate assessment and
consideration of carryover effects

Question 24

What are the advantages of matching according to the lecture

Answer 24

• you can be certain the groups do not differ on the matched variable
• you can guarantee the presence of subgroups - external validity

Question 25

What are the disadvantages of matching according to the lecture?

Answer 25

• groups are still heterogenous
• sometimes pretest required
• you can’t match on all variables
• with drop-out matching is not entirely correct anymore

Question 26

What are you doing by matching?

Answer 26

divide variable with much influence equally over groups

Question 27

What is blocking ?

Answer 27

=limited population

= keep suspect confounder constant

Question 28

What is an advantage of blocking?

Answer 28

you have a homogenous group

Question 29

What is a disadvantage of blocking?

Answer 29

you reduce your external validity

Question 30

What is the Solomon Four-Group Design ?

Answer 30

is good to proof if their is a pretest sensitization or not

Question 31

When to youse Between and when within?

Which question do you have to ask to find out?

Answer 31

1. Is there an order effect?
   if yes; is counterbalancing a solution?
   -yes> check next consideration
   -no > use Between
2. Does counterbalancing lead to more variance in the data than a between-subject design?
   - no >use Within
   - yes > use between
3. How many many participants can you test?
4. How long does testing take?