Tales by Dots and Lines
Numbers pour in from everywhere, match scores, electricity bills, study hours, rainfall, bus fares, and this chapter shows how a scatter of dots and a few lines can turn those numbers into a story you can read at a glance. We revisit the mean with a new image in mind: a see-saw that balances perfectly at one point. From there we uncover tidy rules for how the mean moves when data is added, taken away, shifted, or scaled. The median gets the same careful treatment. Then we practise reading and drawing line graphs, get comfortable with spreadsheets and infographics, decode activity strips, and learn to turn plain tables into clear pictures. The recurring lesson: a good data picture doesn’t only answer a question, it hands you a new one.
Learning Outcomes
By the end of this chapter, you will be able to:
- read the mean in two ways, as a fair share, and as the balance point where the total pull on each side is equal;
- predict how the mean and median respond when values are inserted, deleted, shifted by a constant, or scaled by a factor;
- compute the mean and median quickly from a frequency table, and recover a missing value when the mean is known;
- apply spreadsheet ideas (cells, ranges,
=SUM,=AVERAGE) to arrange and summarise data; - read, interpret, and build line graphs, and pick them wisely for showing change over time;
- make sense of infographics and activity strips, and treat a graph as a launch pad for fresh questions.