# S1 Statistics Revision - Chapter 3 Notes

Chapter 3 - Methods for summarising sample data (location)

- Created by: Megan Wilkinson
- Created on: 17-05-12 17:27

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AS Statistics Revision

Statistics 1 Chapter 3

Methods for summarising sample data (location)

Key points to remember

Mode = the value of a variable that occurs most frequently

Median = the middle value of an ordered set of data.

Quartiles = Divide the data into four equal parts:

25% of the observations are less than or equal to the first

quartile = (n ÷ 4)

50% of the observations are less than or equal to the

second

quartile or median = (n ÷ 2)

75% of the observations are less than or equal to the third

quartile = (3n ÷ 4)

Deciles Divide the data into 10 equal parts

Percentiles Divide the data into 100 equal parts

Box Plot used to represent data and allows comparisons

Smallest Value Largest Value

Q1 Q2 Q3

Population = a collection of individual items or individuals.

Sample = a subset of a population used to represent that

population

Mean = the sum of all observations divided by the total

number

of observations:

x = (x ÷ n) or (fx ÷ f)

Coding = transforms a variable into a simpler one and makes

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