# Background Stats

This section is a summary of the topics you will have covered in GCSE Mathematics.

Types of Data

• Qualitative data (non-numerical, more descriptive e.g. colours)
• Quantitative data (numerical) there are two types for this:
–  discrete; limited to particular values e.g. number of walnuts
continuous; any value within a range e.g. weights of walnuts

Frequency tables are used to summarise large lists:
example 1 – in a survey of 70 families, the number of watermelons owned by each family was recorded in the table below
(discrete data)

example 2 – the lengths of 184 blankets were measured and recorded in the table below with class intervals
(continuous data)

Steam and Leaf Diagrams

A stem and leaf diagram is used to order and present data that is given to 2 or 3 significant figures. It is for lazy people, and also enables the shape of distribution to be revealed for analysis. 2 sets of data can be compared back-to-back using stem and leaf.
Also, individual values of data are preserved.

example 1 draw a stem and leaf diagram using the data in the table below

Weight            Key
13|7                 12|5   means 125 lb
14|56
15|7
16|6
17|47
18| 6

Height                      Key
12|7                          11|4  means 114 cm
13|4
14|8
15|0
16|03
17|
18|15