Exam 5 - One way vs Repeat measures ANOVA

Q: When should you use a one-way ANOVA?

A: When comparing three or more independent groups (different participants in each group).

Q: When should you use a repeated-measures ANOVA?

A: When the same participants are measured in every treatment or at every time point.

Q: What is the easiest way to decide between a one-way and repeated-measures ANOVA?

Ask: Are the same participants in every treatment?

• Yes → Repeated Measures

• No → One-Way

Q: In a one-way ANOVA, how many scores does each participant contribute?

A: One score.

Q: A study compares stress levels among medical, nursing, and pharmacy students. Which ANOVA should be used?

A: One-Way ANOVA (different participants in each group).

Q: A study measures blood pressure before, during, and after meditation using the same participants. Which ANOVA should be used?

A: Repeated-Measures ANOVA (same participants measured multiple times).

Q: Why do researchers often use a one-way ANOVA instead of a repeated-measures ANOVA?

A: Because some treatments cannot be given to the same participants without carryover effects or practical issues.

Q: Which ANOVA controls for differences between participants by calculating SSsubjects?

A: Repeated-Measures ANOVA.

Q: True or False: If participants are randomly assigned to one of three treatment groups, a repeated-measures ANOVA should be used.

A: False. Use a one-way ANOVA because each participant is in only one group.

Q: True or False: If each participant completes all three treatments, a one-way ANOVA should be used.

A: False. Use a repeated-measures ANOVA because the same participants experience every treatment.

Different people = _______ ANOVA. Same people = ___________ ANOVA.

One-Way; Repeated-Measures

In regards to a raw scores table on one-way vs repeated measures ANOVA, what is the difference?

in repeated measures, you are now calculating for the SSsubj and need to get Σ for each subject. This will be used to fine SSsubj

How to find K for raw scores table?

Count horizontally the number of levels next to the subjects

How to find SSsubj?

Σ of every level per subject / K

How to find SStrt?

Σ of one one level for every subject / N

How to find N?

total amount of subjects (or whatever we are investigating)

You just count down vertically

What is needed for raw scores table in one way ANOVA?

ΣX (then summation of this)

ΣX² (then summation of this)

x̄

N (then summation of N)

What is needed for raw scores table in repeated measures ANOVA?

ΣX (then summation of this)

ΣX² (then summation of this)

x̄

N (then summation of N)

AND summation of each level per subject (calculated horizontally - blue arrow)

Which df calculation is the same in one way and repeat measures ANOVA?

df_tot

dftot - N_tot - 1

df_trt calculation in one way vs repeated measures?

One way → K - 1

Repeated → Nk - 1

df_err calculation in one way vs repeated measures?

One way → Ntot - K

Repeated → (Nt-1)(Nk - 1)

df_subj calculation in one way vs repeated measures?

One way → dont need

Repeated → (Nt - 1)

Q: What is Ntotal in an ANOVA?

A: The total number of scores (observations) in the entire experiment.

Q: How do you calculate Ntotal?

A: Add together the number of observations from all treatment groups.

Q: Three treatment groups contain 8, 8, and 8 participants. What is Ntotal?

24

Q: A repeated-measures study has 10 participants measured at 4 time points. What is Ntotal?

A: 40 (10 × 4)

Q: What does K represent in ANOVA?

A: The number of treatment groups (levels of the IV).

Q: Is K the number of participants?

A: No. It is the number of treatments (levels).

Q: A study compares four different diets. What is K?

4

Q: Participants are tested before, during, and after meditation. What is K?

3

Q: What does Nk represent?

A: The number of observations (scores) in a particular treatment group (level).

Q: In a balanced ANOVA, what is true about every Nk?

A: Every treatment group has the same Nk.

Q: A study has four treatment groups with 12 participants in each group. What is Nk?

12

Q: A repeated-measures study has 15 participants measured at five time points. What is Nk?

A: 15 (each treatment contains one score from each participant)

Q: What does Nt represent?

A: The number of participants (subjects).

Q: In a repeated-measures ANOVA, how is Nt different from Ntotal?

A: Nt counts participants only, while Ntotal counts every score collected.

Q: A repeated-measures study has 18 participants measured at three time points. What is Nt?

A: 18

Q: A one-way ANOVA has 24 participants divided into three groups. What is Nt?

24

Q: A one-way ANOVA compares three teaching methods. There are 10 students in each group. Identify K, Nk, and Ntotal.

• K = 3

• Nk = 10

• Ntotal = 30

Q: A repeated-measures study measures 12 participants before, during, and after treatment. Identify Nt, K, Nk, and Ntotal.

• Nt = 12

• K = 3

• Nk = 12

• Ntotal = 36

Q: A study has five treatment groups with 9 participants in each group. Identify K, Nk, and Ntotal.

• K = 5

• Nk = 9

• Ntotal = 45

Q: A repeated-measures experiment has 20 participants measured under four conditions. Identify Nt, K, Nk, and Ntotal.

• Nt = 20

• K = 4

• Nk = 20

• Ntotal = 80

• ___ = All scores

• ___ = Groups/Levels

• ___ = Scores per group

• ___ = People

• Ntotal = All scores

• K = Groups/Levels

• Nk = Scores per group

• Nt = People