# GCSE Statistics Chapter 4 Summary- Summarising Data

After completing this chapter, you will be able to;

- Work out measures of central tendency;
- Find the mean, mode and median of raw data given as a list or as a frequency distribution
- Estimate the mean and median of a grouped frequency distribution and identify the modal class
- Understand the effects of transformations of data on the averages
- Understand when each of these averages is appropriate
- Calculate the weighted mean

- Work out measures of dispersion;
- Work out the range of data given as a list or frequency distribution
- Work out quartiles and percentiles
- Draw box plots
- Identify outliers
- Calculate and use variance and standard deviation
- Compare distributions of data

- Use simple index numbers, chain base index numbers and weighted index numbers;
- Know about the retail prices index.

- Created by: Lottie_Anderson
- Created on: 08-12-12 12:00

First 262 words of the document:

Averages

1.) An average is a single value used to describe a set of data.

2.) The mode is the value that occurs most often.

3.) The median is the middle number in a list after the numbers have been put in

order.

4.) When the number of data values, n, is odd the median is the value of the ½(n

+ 1)th observation.

When n is even the median is the mean of the ½(n)th observation and the ½(n +

2)th observation)

5.) The mean is worked out by adding up the numbers then dividing by how

many numbers there are.

6.) Mean= x

n

Mode, median and mean of discrete data in a frequency table

7.) When discrete data is given in a frequency table:

Mode is the one with the highest frequency

Median = ½(n + 1)th value

Mean = fx

f

Mode, median and mean of grouped data

8.) When information is presented in a table of grouped data, the modal class is

the class with the largest frequency.

9.) For grouped data the median is the value of the 1/2nth observation.

There are two ways of estimating the median

Using the midpoint of a cumulative frequency diagram

Using interpolation

10.) An estimated mean can be found from a grouped set of data using the

formula

Mean = (f x midpoint)

f

Weighted mean

11.) The weighted mean of a set of data is given by

Meanw= wx

w

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