3.6 Analyse data for meaningful patterns and measures  (Page 4/4)

• There are 580 learners at the school. Can you confirm this from the figures in the table?

• A pie chart was made from the breakfast information, and another from the lunch figures. Decide which is which, then fill in the descriptions on the correct slice of each pie chart.

• As you can see, the slices are not all the same size. The sizes are proportional to the number of learners represented in each slice. The way to get them in the right proportions is to calculate the size of the angle at the tip of each slice. For example, 82  580 × 360 = 51°, rounded. This is the angle at the tip of the slice representing the proportion of learners who don’t eat breakfast before coming to school. The formula is: angle size = value  total number × 360. Do the calculations for all five the other slices, and confirm by measurement that the slices are the right size!
• Of course, in the end the slices have to add up to 360°.

5 Scatter plots

• This graph consists only of the plotted points. It links two sets of information on one graph, making comparisons easy. Let’s look at an example.

• The table shows the marks obtained in Science and Maths for a group of 22 learners.

• Here is the scatter plot

For each learner, the coordinates of the point are (Science mark ; Maths mark). Learner A is (75;65). Can you find the dot? Learner B is (45;31), etc. The squares on the paper are not shown, so that the dots can be seen more clearly.

If the dots lie in a pattern (as these do) roughly from bottom left-hand corner to top right-hand corner, then it means there is a connection between the marks a learner gets for the two subjects.

• Those learners, whose marks don’t correlate, are clear from the graph. Find the two circled points. For e x ample, the point (69;95) of learner H, is a little bit higher than the rest of the points. This tells us that the learner has a better Maths than Science mark, but learner B (45;31) does much better in Science than in Maths. If everybody got exactly the same mark for both Science and Maths, then their points would make a very clear pattern. What do you think that pattern would look like?

Assessment