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:
<p><code class="pythonHigh">speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]</code></p>
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 divide the sum by the number of values:
<p><code class="pythonHigh">(99+86+87+88+111+86+103+87+94+78+77+85+86) / 13 =
89.77</code></p>
The NumPy module has a method for this. Learn about the NumPy module in our NumPy Tutorial.
Example
import numpy
speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]
x = numpy.mean(speed)
print(x)
Median
The median value is the value in the middle, after you have sorted all the values:
<p><code class="pythonHigh">77, 78, 85, 86, 86, 86, </code><code class="strong">87</code><code class="pythonHigh">, 87, 88, 94, 99, 103, 111</code></p>
Note: It is important that the numbers are sorted before you can find the median.
The NumPy module has a method for this:
Example
import numpy
speed = [99,86,87,88,111,86,103,87,94,78,77,85,86]
x = numpy.median(speed)
print(x)
Note: If there are two numbers in the middle, divide the sum of those numbers by two.
<p><code class="pythonHigh">77, 78, 85, 86, 86, </code><code class="underlined">86, 87</code><code class="pythonHigh">,
87, 94, 98, 99, 103<br/><br/>
(86 + 87) / 2 = </code><code class="strong">86.5</code></p>
Example
import numpy
speed = [99,86,87,88,86,103,87,94,78,77,85,86]
x = numpy.median(speed)
print(x)
Mode
The Mode value is the value that appears the most number of times:
<p><code class="pythonHigh">99,</code><code class="underlined">86</code><code class="pythonHigh">, 87, 88, 111,</code><code class="underlined">86</code><code class="pythonHigh">, 103, 87, 94, 78, 77, 85,</code><code class="underlined">86</code><code class="pythonHigh"> = 86</code></p>
The SciPy module has a method for this. Learn about the SciPy module in our SciPy Tutorial.
Example
from scipy import stats
speed =
[99,86,87,88,111,86,103,87,94,78,77,85,86]
x = stats.mode(speed)
print(x)
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.
