Sampling a population
To study variation, you only look at a sample of a population.
It would be time-consuming or impossible to catch all the individuals in the group, so samples are used as models for the whole population.
You need to be able to analyse and interpret data.
You may be asked to...
Describe the data, draw conclusions or suggest a reason for the differences.
Standard deviation tells you about the variation within a sample.
The mean value tells you the average of the values collected in a sample.
It can be used to tell if there's variation between samples.. if the mean is vastly different, then there's a lot of variation between the two samples.
Most samples give you a bell-shaped graph - this is called a normal distribution.
The standard deviation tells you how much the values in a single sample vary.
Small standard deviation = little variation, and vice versa.
Good luck on your exams!