Populations, samples and distributions

We will sometimes refer to the sample histogram as the sample distribution. 

There are usually two aspects of these histograms that we are interested in, what is happening on average and the patient-to-patient variation or spread of the data values. The average will be used as a basis for measuring the signal and 

The measures of average that we commonly use are the mean and the median while the standard deviation provides us with our measure of patient-to-patient variation. 

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