The statistical formula for a value's z-score is calculated ... measurement that tells you how far away from the mean (or average) your datum lies in a normally distributed sample.

If there are two middle values the median is halfway between them. This might not be a whole number.

The main averages, which can also be referred to as measures of central tendency, are the mean, mode and median. Robert is preparing for his Mathematics GCSE exams. Each paper is marked out of 100.

Job B is gig work, where you might earn $7,500 one month and $2,000 the next. They have the same average but mean something very different when you are planning your rent or mortgage payments.