Data is another word for information. In KS3 Maths you'll get plenty of practise handling data - analysing information, creating graphs or charts, designing questionnaires. This particular quiz is about averages in data handling and, more specifically, the median value.
There are three generally accepted ways to find the average in a set of data - the mean (the figure found by adding the totals together and then dividing by the number of totals used), the mode (the amount which appears most often) and the median. The median is the set of data which appears in the middle when the data is arranged from lowest to highest.
Though concentrating mainly on median values, this quiz also looks at ranges of values. The range is the difference between the highest and the lowest pieces of data. If you were to look at the number of pets Tom, Dick and Harry have. If Tom has 1, Dick has 2 and Harry has 6 the range would be 5 (6 - 1). The median would be 2 because this is the midmost figure.