maths - statistics 2

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