The Difference Between One-Way Repeated Measures ANOVA and Friedman’s ANOVA

In quantitative research, it is often necessary to compare results from the same participants measured multiple times or under different conditions.

The Difference Between One-Way Repeated Measures ANOVA and Friedman’s ANOVA

For example:

• Measuring performance before, during, and after a training program

• Comparing the effectiveness of three treatment methods on the same group of patients

• Assessing employee stress levels during morning, afternoon, and night shifts

Two common statistical tests are used for this type of repeated measurement: the One-Way Repeated Measures ANOVAand the Friedman’s ANOVA.

Both aim to determine whether there are significant differences across multiple conditions, but their assumptions and appropriate use cases differ substantially.

What Is One-Way Repeated Measures ANOVA?

The One-Way Repeated Measures ANOVA is a parametric test used to compare the means of three or more conditions measured from the same group of participants.It is suitable for analyzing data collected repeatedly from the same subjects under varying circumstances or times.

Key Assumptions

1. The data are normally distributed.

2. The variances of the differences between conditions are approximately equal (Sphericity assumption).

3. All measurements come from the same participants (dependent samples).

Example

Research Topic: “The Effect of Sleep Duration on Memory Performance”

• Independent Variable: Sleep duration (4 hours, 6 hours, 8 hours)

• Dependent Variable: Memory test scores after sleep

If the data are normally distributed and meet statistical assumptions, the One-Way Repeated Measures ANOVA is appropriate to test whether sleep duration significantly affects memory scores.

What Is Friedman’s ANOVA?

The Friedman’s ANOVA is a non-parametric alternative to the One-Way Repeated Measures ANOVA.It is used when the data are not normally distributed or contain outliers that distort the mean.

Instead of comparing actual means, Friedman’s ANOVA uses ranks of data to determine whether there are significant differences among repeated measures.

Example

Research Topic: “Stress Levels of Nurses Across Different Work Shifts”

• Independent Variable: Work shift (morning, afternoon, night)

• Dependent Variable: Stress level (1–5 Likert scale)

If the data are skewed or contain outliers, the Friedman’s ANOVA provides a more reliable analysis because it does not assume normal distribution.

How to Choose Between One-Way Repeated Measures ANOVA and Friedman’s ANOVA

The decision depends mainly on data type and distribution.

• Use One-Way Repeated Measures ANOVA when your data are continuous (interval or ratio) and normally distributed.

• Use Friedman’s ANOVA when your data are ordinal or non-normal, or when outliers are present.

• If the data violate assumptions of normality or sphericity, Friedman’s ANOVA is the safer choice.

• When the assumptions are met, Repeated Measures ANOVA provides stronger statistical power and more detailed comparisons.

In summary:

Use One-Way Repeated Measures ANOVA for continuous, normally distributed data measured multiple times on the same participants.Use Friedman’s ANOVA for ordinal or non-normally distributed data, or when outliers are present.

Why You Should Use Data Investigator

Analyzing repeated-measures data requires both statistical knowledge and technical precision.It involves checking multiple assumptions such as normality, sphericity, and variance equality — and selecting the correct method to avoid misinterpretation or invalid conclusions.

With over 15 years of experience in SPSS-based statistical analysis, Data Investigator provides professional, reliable, and academically sound analysis for both academic and applied research.

Our Services Include

• Conducting accurate data analysis using SPSS

• Testing data assumptions (normality, sphericity, variance equality)

• Applying Repeated Measures ANOVA or Friedman’s ANOVA appropriately

• Providing detailed explanations and interpretations of results

• Issuing official Certificates of Statistical Analysis

Whether you are a thesis student, medical researcher, or government organization,Data Investigator is your trusted partner for accurate, reliable, and professional statistical analysis.

For more information:

E-mail: info@datainvestigatorth.com

Line: @datainvestigator