Idea 1of 22
One number for a whole group
How can one number describe a whole group?
Today you'll discover
- what a typical value is
- where it sits on a line plot
- why the biggest value is rarely typical
Think firstFive readers read 2, 3, 3, 4 and 8 books
Which one number best describes how many books these readers read?
Decide first, then press Next. Look at where the dots bunch up.
A line plot of books read by five readers: dots above 2, 3, 3, 4 and 8. Then markers for the mode and median at 3 and the mean at 4, all among the bunched dots. Then a ring round the dot at 8, far from the rest. The last step shows bus waits of 4, 5, 5, 6 and 5 minutes.
See the whole ideathe big idea and the key word, in one place
The big idea
A typical value is one number that sits where most of the data bunches up.
Easy to get wrongThe biggest value is not the typical one. In 2, 3, 3, 4, 8 only one reader read 8; the other four read 4 or fewer.
Typical in real lifeA typical bus wait, a typical class size, a typical day's rain: each is one number that stands for many.
Key words
- data set
- a group of values collected to answer one question, like how many books each reader read
- typical value
- one number that describes a whole data set, sitting where most of the values are
Ready to use it?
- Pick one number that describes a whole data set.