# maths - statistics 2

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- Created by: shona
- Created on: 27-12-12 12:00

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- maths - statistics 2
- line graphs
- used to show how data changes over a period of time
- can be used to show trends
- such as the average daily temperature changes over the year

- data points on line graphs can be joined by lines
- when the lines join points that show continuous data they are drawn as solid lines because the lines are used to estimate intermediate values
- when the lines join points that show discrete data they are drawn as dotted lines because the lines cant be used to estimate intermediate values

- stem and leaf diagrams
- when data is first recorded it is called raw data and in unordered
- unordered data can be put into order to make it easier to read and understand this is called ordered data
- stem and leaf is a way of showing ordered data

- unordered data can be put into order to make it easier to read and understand this is called ordered data
- the stem is the number on the left of the vertical ine
- the leaves are the numbers on the right of the vertical line
- the mode is the most common entry
- to find the median you count from the start to the middle value
- find the range by subtracting the lowest value from the highest
- find the mean by adding all the values and dividing by the number of values in the table

- when data is first recorded it is called raw data and in unordered
- scatter diagrams
- a diagram that compares to variables
- the variables are plotted as coordinates

- the scatter diagram will show a relationship between variables if there is one
- the relationship is described as correlation and can be written as a real life statement
- a line of best fit can be drawn through the data
- the line of best fit can be used to predict the value of one variable when the other is know

- a diagram that compares to variables
- cumulative frequency and box plots
- cumulative frequency diagrams
- the interquartile range is a measure of dispersion of a set of data
- the interquartile range estimates extreme values and bases that measure of spread on the middle 50% data
- the interquartile range and the median can be found by drawing a cumulative frequency diagram
- add the frequency to the sum of the preceding frequencies to find the cumulative frequency

- box plots
- another way of comparing data is the box plot
- box plots can be used to show the spread of two or more sets of data and make it easier to compare data
- a box plot requires five pieces of data
- the lowest value of the set of data
- the lower quartile
- the median
- the upper quartile
- the highest value of the set of data

- cumulative frequency diagrams

- line graphs

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