Basic science: understanding numbers

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# 3.1 Absolute numbers don’t tell you everything

Figure 1

The previous two weeks have shown the important role numbers play in our lives, and their use in scientific investigations, such as estimating the impact of the Greenland ice sheet melting. Sometimes, just presenting the number is not particularly useful, and can lead to long-winded analogies, such as how many swimming pools of bottled water we drink each year – have you remembered that number yet? However, there are some ways of presenting numbers that help show results in a more meaningful way.

Let’s imagine a scientist is interested in the water content of three different fruits: watermelon, cucumber and peach. The experiment involves measuring the initial weights of the fruits, then slowly drying each one out in an oven and measuring the final weights. Assuming that the fruits didn’t burn, only water is lost during the drying process. The difference between the start and end weights tell the scientist how much water the fruits contained.

The scientist wrote the results down in a table:

## Table 1 The water content of different fruits (g)

Fruit Weight before (g) Weight after (g) Water contained in fruit (g)
Watermelon 160.156 16.295 143.861
Cucumber 127.751 7.472 120.279
Peach 64.375 8.681 55.694

The amount of water in each fruit has been correctly determined and technically there is nothing wrong with these results. It is clear to see that the watermelon contained the most water, while the peach contained the least water. However, because their starting weights were different it is less easy to tell which of the three fruits contained the largest proportion of water, which is the number that would actually help us understand the results best.

This week is all about learning how to talk about numbers, and how to present them in a way that makes the meaning and implication clear. You will be shown how our scientist’s results can be presented in ways that make sense. The topics in this week are all tools to help convert numbers into a more useful and meaningful format.

All of the topics covered are widely used and have applications in both everyday life and in further scientific study.

As you work through this week, think about where you may have used these techniques or seen numbers presented in these ways. Did you realise what the numbers meant or how they were obtained? Think about where these techniques could be useful and whether you would now be more confident using them.

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