Representation of Data

Introduction Data are pieces of numerical and other information. Statistics concerns itself with the collection, organisation and analysis of data. Data is collected by observing or measuring some property.

Qualitative V Quantitative Qualitative variables take non- numerical values. Quantitative variables take numerical values.

Continuous V Discrete A continuous quantitative variable can take any value in a given range. A discrete quantitative variable has clear ‘gaps’ between the values it may take.

Stem-and-leaf diagrams It is very difficult to draw conclusions from lists of raw data. A stem-and-leaf diagram attempts to recognise some pattern or order in the data.

Do Exercises 1A pp.8-9

Large data sets For large data sets stem-and- leaf plots may be come too unwieldy. It may be better to gather such data into groups, called classes, and display the results graphically as a histogram.