Understanding statistics and numbers – EXERCISES

Exercise: Budget breakdown

Goal: demonstrate that numbers are easier to understand when broken down and put into context

Materials: printed sheets

Time: 5 minutes

In this exercise, the class votes with their feet on what they think is the correct Health budget. Prepare by labelling sheets of paper with incremental sums of money: $1 million, $10 million, $100 million, $1 billion, and so forth up to $10 trillion. Paste these around the room.

Ask students to stand in front of the sum which they think is closest to the annual Health budget. Once they’ve made their choice, have them peel off the sheet to reveal another underneath, showing the value of that sum in terms of cost per person per year. In this case, $1 billion would equate to $44 per person, per year.

Ask the students if they’d like to revise their choice and stand in front of a different sum. Once they have moved, peel away those sheets to reveal another series underneath, showing cost per person per week. An annual budget of $1 billion equates to 86c per person per week. Ask the students if they are happy with their final choice.

Typically the class will converge on the correct figure as the exercise progresses. This neatly demonstrates how large numbers can throw us off, and that breaking them down into logical units can help us to get to grips with them. The exercise can be replicated with any large sum that can be put into context in this way – military and education budgets, national energy and water consumption, number of photos uploaded to Facebook – your imagination is the limit.


Exercise: Quiz on risk

  1. Breast cancer screening by mammography lowers risk of dying for women around sixty by 25 percent. About 4 in 1000 women in this age group die of breast cancer. Can you rephrase the percentage? What number gives a better idea of what’s going on?
    ANSWER: Without screening, 4 in 1000 women will die prematurely of breast cancer, with screening, 3 in 1000.
  2. Correlation does not equal causation — the fact that two phenomena are related, does not mean that one is the cause of the other. To practice: Taller people earn more than shorter people. Why would that be?
    ANSWER: Men are, on average, taller than women, and men earn, on average, more than women.


Thanks to the World Federation of Science Journalists