Mathematics for IGCSE & O level - Categorical, Numerical And Grouped Data (Section 8 - No. 9)
Why is it often impossible to find out some statistical information?
Because some people won't give their personal information
Because of the cost of running a survey
Because you cannot find out from everyone
Because some data is not useful.
Forklaring
When you try to find some statistical information, it is often impossible to find out from everyone