Basic Data Concepts

Data are facts or figures collected to learn something. We sort data by type, count it with tallies, and show it in tables and charts.

Key ideas

Data can be numbers, text, images or sounds: heights are number data, a photo is image data.
Tally marks count in groups of five, so a long list can be counted quickly and checked.
In a pictograph each picture stands for a fixed number; half a picture stands for half of it.
Tables organise data in rows and columns; bar graphs compare amounts; pie charts show parts of a whole.
The mode is the item that appears most often; the range shows how spread out numbers are.
Sorting data, smallest to largest or the other way, makes it easy to find a value in a given place.

Remember

Range	largest value − smallest value
Mode	the value that appears most often
Pictograph	number of pictures × value of one picture
Tally	four strokes with one across = 5
Data from asking people	a survey

Watch out

Forgetting the key of a pictograph and counting pictures instead of what they stand for.
Finding a place in a list before sorting it.
Giving how many times the mode appears instead of the mode itself.

Worked example

(a) Children chose their favourite fruit: banana, grapes, orange, grapes, banana, banana, banana, mango, banana, orange, banana, banana, orange, orange, grapes. How many chose banana?
(b) Goals scored in 7 matches: 12, 21, 8, 21, 16, 15, 23. What is the mode?

Working: (a) banana 7, mango 1, orange 4, grapes 3; (b) 21 appears 2 times

Answer: (a) 7; (b) 21