Reading-And-Interpreting-Statistical-Diagrams Wjec-Eduqas Foundation

Reading & interpreting statistical diagrams

How do I interpret statistical diagrams?

• Read and understand the initial sentences describing the situation (context)

  • Underline important words if necessary

• Look for any keys that may help you to understand the diagram

  • For example

    • 1 unit represents 20 people

    • Year 10 is the solid line, Year 11 is the dotted line

    • Class A is shaded, class B is striped

• Read the titles of diagrams and all axes labels 

  • A graph for ‘new students at a school’ is different to ‘all students at the school’

  • A frequency axis that starts at 50 is different to one starting at 0

• Understand which units are being used

  • Individual lengths may be in centimetres but total length may be in metres

  • Populations may be measured in thousands

• Look out for any extreme values (outliers / anomalies)

  • One month’s temperature might be unusually high

    • Was it a heat wave or a recording error?

How do I draw conclusions from diagrams?

• Look for overall trends in the diagram

  • Prices increase year on year

  • The temperature peaks in June

• Use numbers from the graphs

• Refer to any changes

  • The steepness (gradient) of graph may change

• Write in full sentences that copy the exact wording from the question

  • ‘The number of goats in farm A has decreased by 12 over the 8 month period’

  • Not ‘There are fewer of them now’

• You may need to calculate the mode, median, mean or range to support any explanations

• Understand why drawing conclusions may not be suitable

  • The data set may be too small to be representative

  • The data set may be biased

  • Consider the scope of the data

    • e.g. Data for January to March cannot be used to predict August