Elementary Statistics: Collecting, Recording and Representing Data
Statistics begins with collecting reliable information, recording it clearly and selecting a suitable representation.
Collecting and recording
Data are facts or measurements collected for a purpose. Decide what is being measured, identify the population or sample, use a fair method and record observations in a tally or frequency table. Qualitative data describe categories; quantitative data are numerical.
Representation
- Bar charts compare separate categories; bars have equal widths and gaps.
- A pictogram uses a key, so every symbol must be interpreted using that key.
- A line graph shows change over an ordered scale. Label axes, include units and choose a suitable scale.
Worked example
If a tally records 6 learners choosing football, 4 choosing volleyball and 5 choosing athletics, the total frequency is 15. A bar chart should have the sports on the horizontal axis and frequency on the vertical axis.
Practice
- Design a tally table for the colours chosen by 20 learners.
- Represent a frequency table using a labelled bar chart.
- Explain why a misleading scale can distort the message of a graph.
