Analysing data - OCRMedian

The median is the value of the middle item of data when all the data is arranged in order. If there are two middle items of data, then the median is halfway between their two values.

To find the median, you can arrange the data in ascending order and work towards the middle by crossing off numbers at each end.

Or you can add 1 to the number of items of data and then divide by 2 to find which item of data will be the median.

Example

7 babies weigh the following amounts:

2.5 kg, 3.1 kg, 3.4 kg, 3.5 kg, 3.5 kg, 4 kg, 4.1 kg

Find the median weight of the babies.

Using the first method:

The data is already in order. Cross off the first and last item of data (the items in bold):

2.5 kg, 3.1 kg, 3.4 kg, 3.5 kg, 3.5 kg, 4 kg, 4.1 kg

Repeat until you reach the middle item of data:

3.1 kg, 3.4 kg, 3.5 kg, 3.5 kg, 4 kg

3.4 kg, 3.5 kg, 3.5 kg

3.5 kg

The median weight of these babies is 3.5 kg.

Using the second method:

2.5 kg, 3.1 kg, 3.4 kg, 3.5 kg, 3.5 kg, 4 kg, 4.1 kg

The median weight of these babies is 3.5 kg.

If another baby weighed 3 kg then the list would be:

2.5 kg, 3 kg, 3.1 kg, 3.4 kg, 3.5 kg, 3.5 kg, 4 kg, 4.1 kg

Now there are two items of data in the middle, so the median is the value halfway between 3.4 kg and 3.5 kg, which is 3.45 kg.

The median weight of these 8 babies is 3.45 kg.