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
      • 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


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