Understanding Data

About this unit

Data is everywhere: marks, sales, weather readings and app usage. This unit looks at why data matters, how it is collected and stored, and how simple statistics summarise it. You will calculate measures of central tendency (mean, median, mode) and of spread (range, variance, standard deviation), and use them to interpret data and draw sensible conclusions.

Key ideas

• Data can be structured (in rows and columns) or unstructured (text, images, audio, video).
• Data is collected from primary sources (first-hand) or secondary sources (already collected).
• Storage options include hard disks, solid state drives, pen drives and cloud storage.
• Mean, median and mode describe the centre of the data.
• Range, variance and standard deviation describe how spread out the data is.
• Outliers can distort the mean more than the median.

How to prepare

Practise calculating each measure by hand for small data sets of 5 to 8 values, and check them in Python with the statistics module. Learn when the median is a better summary than the mean. Expect short numericals and situation-based questions on choosing a measure.