Secondary National Strategy Handling Data

1. Secondary National StrategyHandling Data Graphs and charts Created by J Lageu, KS3 ICT Consultant – Coventry Based on the Framework for teaching mathematics pages 248 - 275

2. Graphs & charts a handy guide Click on the required choice • Types of data • Types of graph or chart Return to last slide viewed Return to category menu KS3 Handling Data

3. Data types • Categorical • Discrete • Continuous • Grouped discrete • Grouped continuous • Means KS3 Handling Data

4. Categorical • data is broken into categories, there is no order to the categories eg • gender - male, female • transport method – walk, bus, train etc • possible graph & chart choices • pie chart • bar chart • compound bar chart • bar line graph • pictogram KS3 Handling Data

5. Discrete • data is numerical with separate values • counted eg no of letters in a word, no on a dice • ordered but not counted eg school year group, size of shoe • possible graph & chart choices • pie chart • bar chart • compound bar chart • bar line graph • pictogram KS3 Handling Data

6. Continuous • data is numerical and is measured • length, weight, time etc. • even if there is rounding, say to the nearest hour, it is still continuous. We are approximating, but there is still meaning to in between points. • digital clock is continuous because it approximates. • exception - shoe size is discrete because it is labelling a type of shoe. There are only ever a certain number of shoe sizes and there is no shoe size between 3 & 3½. • possible graph & chart choices • frequency diagram • frequency polygon • line graph • scatter graph • cumulative frequency diagram KS3 Handling Data

7. Grouped discrete • discrete data grouped into suitable class intervals • intervals should be equal • there should be no overlap eg 0-5, 5-10 etc is wrong, where does 5 go? • unequal intervals makes the data categorical eg ages: 0-5, 6-10, 11-16, 17-21, over 21 • possible graph & chart choices • bar chart • compound bar chart KS3 Handling Data

8. Grouped continuous • continuous data grouped into suitable class intervals • intervals usually equal • there should be no overlap eg 0 < t < 5, 5 <= t < 10 • un-equal intervals need histograms, post KS3 • possible graph & chart choices • frequency diagram • frequency polygon • line graph • cumulative frequency diagram KS3 Handling Data

9. Mean • mean calculated for continuous data normally over a period of time eg monthly average • possible graph & chart choices • line graph KS3 Handling Data

10. Types of graph and chart • Pie chart • Bar chart • Compound bar chart • Bar-line graph • Pictogram • Frequency diagram • Frequency polygon • Line graphs • Scatter graph • Cumulative frequency diagram KS3 Handling Data

11. Pie chart • 3D distorted are not strictly correct, because the angle should be proportional to the frequency avoid unless you have a specific purpose KS3 Handling Data

12. Main form of travel to school: pupils aged 5 to 10 Bar chart legend • Notice the gaps between the bars • Labels in the middle of the bars two bars per category grouped data KS3 Handling Data

13. Compound bar chart key • Notice the gaps between the bars labels on bars KS3 Handling Data

14. Bar-line graph • The length of the bar represents the frequency. • What is being counted or measured (the independent variable) is placed on the horizontal axis, and the count or measure (the dependent variable) on the vertical axis. • It is not appropriate to join the tops of the bars. KS3 Handling Data

15. Pictogram • all symbols should be the same size & shape • fitness for purpose may justify differences, but size must be the same scale half picture=1 mathematically incorrect identical pictures KS3 Handling Data

16. Frequency diagram • Notice there are no gaps between the bars indicating non-zero start labels start & end of bars see frequency polygon KS3 Handling Data

17. Frequency polygon • Points are plotted at the middle of the range if grouped see frequency diagram KS3 Handling Data

18. Line graph data point middle month & year labels KS3 Handling Data

19. Scatter graph – two variables line of best fit KS3 Handling Data

20. Cumulative frequency diagram median KS3 Handling Data