# Quantile - (Median|Middle)

### Table of Contents

## 1 - About

The median is a measure of center. The middle number of a set of data is the median.

This measure is resistant.

The median is a 50th percentile (or “middle” quartile). Half of the data is below the median.

## 2 - Articles Related

## 3 - How to calculate a median ?

### 3.1 - With an uneven number of numbers

- Score: 7, 5, 8, 9, 5
- Ordered Score (after a sort): 5, 5, 7, 8, 9

The middle number is the third score, or 7, so the median of this data is 7.

### 3.2 - With an even number of numbers

- Score: 5, 8, 9, 5
- Ordered Score: 5, 5, 8, 9

When there is an even number of numbers, there is no true value in the middle.

The median is then the mean of the two middle numbers of (5 + 8)=13/2 = 6,5.

If there are four students sitting in a row, the middle of the row is halfway between the second and third students.

## 4 - Example

### 4.1 - Python

```
def median(sequence):
isEven = True
if len(sequence) % 2 == 0:
isEven = True
else:
isEven = False
sequence.sort()
# - 1
index_average = int(round(len(sequence)/2))
if isEven:
median = (sequence[index_average-1]+sequence[index_average])/2.00
else:
median = sequence[index_average]
return median
```