Pie Charts Histograms


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Pie Charts Histograms

  1. 1. Why pie charts?<br /><ul><li>A pie charts is a good way of displaying data when you want to show how something is shared or divided.</li></ul>Rough grazing<br />crops<br />crops<br />Permanent grass<br />Wood land<br />Towns and roads<br />Land use in the UK<br />
  2. 2. How do we calculate angles?<br /><ul><li>20 000 students took part in a survey on cheese</li></ul>10 566 students answered blue.<br />10 566 x 360º = 190º (to 3 s.f.)<br />20 000<br />How do we calculate frequency (number of people) ?<br />Measure the angle with a protractor if you are not given it.<br />47º x 20 000 = 2610 people (to 3 s.f)<br />360º<br />….<br />
  3. 3. Bar Charts (too easy)<br />A bar chart is a chart where the height of bars represents the frequency. <br />The data is &apos;discrete&apos; (discontinuous- unlike histograms where the data is continuous)<br />The bars should be separated by small gaps.<br />Frequencyisalwaysonthe y-axis<br />
  4. 4. Histograms<br />When the data is continuous (time, length, anything numerical) the graph is called a histogram.<br />A histogram with equally spaced bars looks exactly like a bar chart.<br />BUT you can draw histograms with bars of different widths and the area of the bar is what’s important. Frequency Density is the label for the y-axis. <br />Frequency density = frequency <br /> class width<br /> ‹ VeryImportant<br />…<br />
  5. 5. 5<br />4<br />3<br />frequency density<br />2<br />5<br />?<br />0<br />1<br /> 1<br />6<br />10<br />8<br />9<br />3<br />1<br />2<br />4<br />5<br />7<br />0<br />Distance (Miles)<br />Example Question: The table shows the distance walked in kmsby some walkers at Collserollaat the weekend. Draw a histogram for the data.<br />5<br />2<br />5  1 = 5<br />4<br />2  1 = 2<br />3<br />12  3 = 4<br />1.25<br />3  1 = 3<br />1. The class widths are unequal so a frequency density column is needed.<br />5  4 = 1.25<br />2. Scale the horizontal axis.<br />3. Calculate frequency densities and scale the vertical axis.<br />
  6. 6. 5<br />Distance Walked by Walkers<br />4<br />3<br />frequency density<br />2<br />1<br />6<br />10<br />8<br />9<br />3<br />1<br />2<br />4<br />5<br />7<br />0<br />Distance (Miles)<br />Example Question 2 The table shows the distance walked in kmsby some walkers at Collserollaat the weekend. Draw a histogram for the data.<br />5<br />2<br />4<br />3<br />1.25<br />4.Draw in the bars and title.<br />
  7. 7. Scattergraphs<br />We use scattergraphswhenwehavetwo sets of data.<br />Eg Are peoplewho are good at maths<br />alsogood at science?<br />Are peoplewho are older, <br />taller?<br />Wehaveone set of valuesonthe x-axis and theotheronthe y-axis<br />
  8. 8. Practice 1: Look at the following scatter diagrams. Do they have positive or negative correlation and what does that mean?<br />1a) (b)<br />Next <br />
  9. 9. 2) The table lists the weights of twelve books and the number of pages in each one.<br />On the grid, draw a scatter graph to show the information in the table.<br />Draw a line of best fit on the graph and then describe the correlation between the number of pages in the book and their weight.<br />How much would you expect a book of 120 pages to weigh?<br />