Pictograms and tally charts (age 11+)
Construct and interpret frequency tables, bar charts, pie charts, pictograms, and vertical line charts for both categorical and grouped numerical data, choosing appropriate representations for the data type
What a learner can do afterwards
- Construct a grouped frequency table from raw continuous data, choosing appropriate class intervals
- Draw a pie chart by calculating the angle for each category
- Interpret a bar chart comparing two data sets and draw a conclusion about the difference
The lesson
Not every set of data fits the same chart. Categories, like favourite drinks or types of pets, work well as bar charts, pie charts, or pictograms. Numbers that can take any value, like height or time, need extra work first: you group them into class intervals before you can chart them at all.
A class of 20 students voted for their favourite drink: tea 5, coffee 3, juice 8, water 4. To turn each vote count into a pie chart angle, divide it by the total and multiply by 360. Juice got the most votes, so 8 divided by 20 times 360 equals 144 degrees, the biggest slice of the circle.
When you group continuous data, like the heights of 30 plants, keep every class interval the same width and make sure they don't overlap or leave gaps. Around 5 to 8 groups usually keeps the table clear. Too many groups and the pattern gets lost; too few and you hide the detail.
Match the chart to the data: group continuous numbers into fair class intervals, share out a pie chart by angle, and read bar heights carefully before you compare them.
Watch it
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.