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 divide 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. Learn about the NumPy module in our NumPy Tutorial.
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)
Try it Yourself »
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)
Try it Yourself »
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. Learn about the SciPy module in our SciPy Tutorial.
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)
Try it Yourself »
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.
