Unit 2: Patterns in Data

Standard

 Mean

The mean is the average of the numbers.

It is easy to calculate: add up all the numbers, then divide by how many numbers there are.

Absolute Value

Absolute Value means …

… only how far a number is from zero:

“6” is 6 away from zero,
and “−6” is also 6 away from zero.

So the absolute value of 6 is 6,
and the absolute value of −6 is also 6

Go over Absolute Value and do some practice (the website checks it)

Mean Absolute Deviation

Mean absolute deviation (MAD) is about calculating the average distance from the mean.

MAD BURGER!!!
MAD Burger

Click here to watch a video from our 8th Grade Math textbook that goes in to detail and explain how to calculate the MAD.

MEAN ABSOLUTE DEVIATION:

The average/mean distance from the average/mean is the MAD.

Yes, we use “mean” twice: Find the mean … use it to work out distances … then find the mean of those!

Three steps:

  • 1. Find the mean of all values
  • 2. Find the distance of each value from that mean (subtract the mean from each value, ignore negative signs)
  • 3. Then find the mean of those distances

Like this:

Example: Find the Mean Absolute Deviation of

3, 6, 6, 7, 8, 11, 15, 16

Step 1: Find the mean:

Mean = 3 + 6 + 6 + 7 + 8 + 11 + 15 + 16   = 72   = 9
8 8

Step 2: Find the distance of each value from that mean:

Value Distance from 9
3 6
6 3
6 3
7 2
8 1
11 2
15 6
16 7

Which looks like this:

Step 3. Find the mean of those distances:

Mean Deviation = 6 + 3 + 3 + 2 + 1 + 2 + 6 + 7   = 30   = 3.75
8 8

So, the mean = 9, and the mean deviation = 3.75

It tells us how far, on average, all values are from the middle.

In that example the values are, on average, 3.75 away from the middle.

For deviation just think distance

MEAN ABSOLUTE DEVIATION Practice Problems:

Click here or here to practice Mean Absolute Deviation online and get automatic feedback (it grades it)! 🙂

Get your MEAN ABSOLUTE DEVIATION on!

Random Sample

This is where everyone has an equal and fair chance of being selected.

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