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# Machine Learning - Mean Median Mode

## Mean, Median, and Mode

What can we learn from looking at a group of numbers?

In Machine Learning (and in mathematics) there are often three values that interests us:

• Mean - The average value
• Median - The mid point value
• Mode - The most common value

Example: We have registered the speed of 13 cars:

`speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]`

What is the average, the middle, or the most common speed value?

## Mean

The mean value is the average value.

To calculate the mean, find the sum of all values, and dived the sum by the number of values:

```(99+86+87+88+111+86+103+87+94+78+77+85+86) / 13 = 89.77```

The NumPy module has a method for this:

### Example

Use the NumPy `mean()` method to find the average speed:

import numpy

speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]

x = numpy.mean(speed)

print(x)
Run example »

## Median

The median value is the value in the middle, after you have sorted all the values:

`77, 78, 85, 86, 86, 86, ``87``, 87, 88, 94, 99, 103, 111`

It is important that the numbers are sorted before you can find the median.

The NumPy module has a method for this:

### Example

Use the NumPy `median()` method to find the middle value:

import numpy

speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]

x = numpy.median(speed)

print(x)
Run example »

If there are two numbers in the middle, divide the sum of those numbers by two.

`77, 78, 85, 86, 86, ``86, 87````, 87, 94, 98, 99, 103 (86 + 87) / 2 = ````86.5`

### Example

Using the NumPy module:

import numpy

speed = [99,86,87,88,86,103,87,94,78,77,85,86]

x = numpy.median(speed)

print(x)
Run example »

## Mode

The Mode value is the value that appears the most number of times:

`99,``86``, 87, 88, 111,``86``, 103, 87, 94, 78, 77, 85,``86`` = 86`

The SciPy module has a method for this:

### Example

Use the SciPy `mode()` method to find the number that appears the most:

from scipy import stats

speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]

x = stats.mode(speed)

print(x)
Run example »

## Chapter Summary

The Mean, Median, and Mode are techniques that are often used in Machine Learning, so it is important to understand the concept behind them.