Collecting and Checking Data
Acquire, validate and represent data for nominal and ordinal categorical and discrete numerical variables, to address a question of interest or purpose using software including spreadsheets; discuss and report on data distributions in terms of highest frequency (mode) and shape.
Read this first
Collect the data carefully. Then check it before you use it.
Soccer has the highest bar. That is the mode.
Words you need
- Mode
- The answer that came up most often.
- Validate
- Check the data is sensible.
- Category
- A group the data falls into.
Worked example
e.g. You collect ages: 10, 11, 10, 110, 11. What do you do?
- Look at every value before you use it.
- 110 is not a sensible age for a class.
- Go back and check. It was meant to be 11.
- Fix it, then find the mode. It is 11.
Never use data you have not checked. One wrong value spoils the whole set.
Practice
The pictures fade as you go. By the last few you are on your own.
1What is the mode of this data?with a picture
AnswerSoccer.
2How many children were asked?with a picture
Answer23.
3A height reads 1500 cm. Is that sensible?with a hint
Need a hint?
That would be 15 metres.
AnswerNo. It is probably 150 cm.
4What is the mode of 3, 5, 3, 7, 3?with a hint
Need a hint?
Which value appears most?
Answer3.
5Can a set of data have two modes?on your own
AnswerYes, if two values tie for most common.
6Why check data before making a graph?on your own
AnswerA wrong value makes the graph wrong too.
7Name one way to record data quickly.on your own
AnswerA tally chart or a spreadsheet.
Think about it
1
What does the shape of the data tell you?
One good answerWhere most answers sit, and whether any are unusual.
2
Why is the mode useful for categories?
One good answerYou cannot find a mean of colours or sports.
Common mistakes
Using data without checking it.
One silly value can change the whole picture.
Thinking the mode is the middle.
The mode is the most common, not the middle.