What is an estimated mean?

Answer 1

Answer

If it's not possible (e.g. too time consuming or expensive) to study a whole population you can make certain inferences by taking a valid, smaller sample.

Your sample mean is your estimate of the true population mean. The sample mean is usually expressed in terms of a confidence interval to indicate that there's a degree of uncertainty around the estimate.

Here is an Example :

Stratified Mean

Boys Girls Total

Year 7 128 132 260

Year 8 122 158 280

Total 250 290 540

There is a questionnaire on at a school. They want to ask 50 pupils altogether.

To work out Year 7 Boys you would do 50(128/540) or in a simpler form 128 divided by 540, then times the answer by 50. This would give you 11.851851851… but you can just round it up to 12. You want to be careful though, as if you always round up or down your total might not match your original total.

To work out Year 8 altogether you do 50(280/540) or 280 divided by 540, then times the answer by 50.

Simple as that :D