# Topic 1: Organizing Data

- Created by: Lulu
- Created on: 16-03-15 19:02

First 276 words of the document:

1|Organising data

Raw data the data collected

Stem and leaf diagram single data or back-to-back data

5|468 means 54,56,58 730 |2means 20,23,27

Always use a key

Discrete data possible values are separated by gaps , eg 1, 1.5, 2, 2.5,...

Continuous data comes from measurement, eg 29.8, 29.9, 32.0, 24.3

Grouping grouping similar data together to make it easier to manipulate

Eg. The group 10-19 contains all the data between 9.5 and 19.5

Ahistogramshows the frequency through its area

frequency

f requency density = width of interval

The frequency densityis shown on the vertical axis

f requency = width of interval ×frequency density

When values are ordered highest to lowest:

Median middle value, can be used as the `average'

o If there are two values in the centre, the median is halfway between the two

Range difference between highest value and lowest value affected by extreme values

at upper and lower ends, which distort the entire picture

Lower quartile Q1,

has 1

4 of the values less than or equal to it, so can be found halfway

between n n

4 th and ( 4 + 1) th value

Upper quartile Q , has 3 of the values less than or equal to it, so can be found halfway

3 4

between 3n th and (34n + 1) th value

4

o When finding quartiles, always round up

The median is Q 2

Interquartile range(IQR) is Q3 - Q1 and

tells us the spread of the `middle half' of the data

o This excludes extreme values and is a better measure of spread

The quartiles can be show using a box plot

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