Mean Absolute Deviation (MAD) Formula

The Mean Absolute Deviation (MAD) is the average of the absolute distances between each data point and the mean of the dataset.

The Formula

MAD=∑∣x−xˉ∣n

When to use: Find how far each number is from the mean (ignoring +/-), then average those distances. It tells you: on average, how far is a typical value from the center?

Quick Example

Data: 2, 4, 6, 8. Mean = 5. Distances from mean: 3, 1, 1, 3. MAD=3+1+1+34=2

Notation

MAD stands for Mean Absolute Deviation. ∣xi−xˉ∣ is the absolute deviation of the ith data point from the mean xˉ.

What This Formula Means

The Mean Absolute Deviation (MAD) is the average of the absolute distances between each data point and the mean of the dataset. It measures how spread out data values are from the center, with larger MAD values indicating more variability.

Find how far each number is from the mean (ignoring +/-), then average those distances. It tells you: on average, how far is a typical value from the center?

Formal View

For a dataset {x1,x2,…,xn} with mean xˉ, the Mean Absolute Deviation is MAD=1n∑i=1n∣xi−xˉ∣.

Worked Examples

Example 1

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Find the MAD of 3,5,7,9.

Answer

2

First step

1
Mean =(3+5+7+9)/4=6.

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Example 2

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A class has temperatures 68,70,72,70,70 (∘F). Find the MAD.

Example 3

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Data 1,2,3,4,100 has mean 22. Find the MAD.

Common Mistakes

  • Forgetting absolute value - The safer move is to ask "Do I need one number that represents the center of the data, and have I checked whether extreme values change that choice?" and then state the data source, denominator, or variable before interpreting the result.
  • Dividing by wrong number - The safer move is to ask "Do I need one number that represents the center of the data, and have I checked whether extreme values change that choice?" and then state the data source, denominator, or variable before interpreting the result.
  • Confusing with standard deviation - The safer move is to ask "Do I need one number that represents the center of the data, and have I checked whether extreme values change that choice?" and then state the data source, denominator, or variable before interpreting the result.
  • Choosing mean absolute deviation (mad) from a keyword alone - Keywords like average, typical, middle are only clues; the data structure must match the concept.

Why This Formula Matters

Mean Absolute Deviation (MAD) gives students a disciplined way to summarize how spread out data is. It is especially useful when two data sets share the same center, because MAD reveals which one is more variable and therefore less predictable.

Frequently Asked Questions

What is the Mean Absolute Deviation (MAD) formula?

The Mean Absolute Deviation (MAD) is the average of the absolute distances between each data point and the mean of the dataset. It measures how spread out data values are from the center, with larger MAD values indicating more variability.

How do you use the Mean Absolute Deviation (MAD) formula?

Find how far each number is from the mean (ignoring +/-), then average those distances. It tells you: on average, how far is a typical value from the center?

What do the symbols mean in the Mean Absolute Deviation (MAD) formula?

MAD stands for Mean Absolute Deviation. ∣xi−xˉ∣ is the absolute deviation of the ith data point from the mean xˉ.

Why is the Mean Absolute Deviation (MAD) formula important in Statistics?

Mean Absolute Deviation (MAD) gives students a disciplined way to summarize how spread out data is. It is especially useful when two data sets share the same center, because MAD reveals which one is more variable and therefore less predictable.

What do students get wrong about Mean Absolute Deviation (MAD)?

Students often know a procedure related to mean absolute deviation (mad) but skip the recognition step: Do I need one number that represents the center of the data, and have I checked whether extreme values change that choice? That leads to a calculation or graph that looks reasonable but answers a different question.

What should I learn before the Mean Absolute Deviation (MAD) formula?

Before studying the Mean Absolute Deviation (MAD) formula, you should understand: mean fair share.

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