An introduction to design engineering
An introduction to design engineering

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An introduction to design engineering

4.6 Designing for people using numbers

Designing for people can be a complex process for some very simple reasons. Designing the height of a desk for one person might be relatively straightforward, but making that same desk suit lots of people is quite difficult because of the variation in human sizes.

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Figure 17 There are many variations to consider in any design and different variations matter to different people

Playing with data

The data you have just been looking at could now be added to hundreds, thousands and even millions of additional data points. In fact, some of the anthropometric data used in the British Standards is collected from entire country populations.

Each time another point is added, the shape of the histogram will change slightly. If we had enough data points we could even imagine the histogram being quite a smooth shape (Figure 18).

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Figure 18 Dynamic illustration of a smoother shape emerging with enough data points

The smooth curve in Figure 18 is called a distribution curve. This is one of a number of different types of representation of data that is useful to be aware of. It’s different to the histogram in Activity 11 because it is smooth (continuous) and is not divided into individual (discrete) ranges of data.

It is simply useful to see the shape of this data and to realise that a visual representation of information can be just as useful as a mathematical one.

Now you will explore this in the final activity.

Activity 14 Playing with UK height data

Allow 20 minutes to complete this activity

In the interactive graph below you can see the distribution of male and female heights in the UK population. The horizontal axis shows heights (in metres) and the vertical direction represents the number of people in the population.

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Interactive feature not available in single page view (see it in standard view).
  1. First, select either the ‘Male’ or ‘Female’ population. Next, adjust the left and right vertical bars (labelled ‘A’ and ‘B’) and place them in an approximately symmetrical position in the middle of the graph. Then use the adjustment arrows to nudge the numbers (shown above the graph) and get them to show around 50% of the population (pay attention to the dynamic percentage information immediately above the graph).

    • a.What is the height range of roughly 50% of the male population?
    • b.What is the height range of roughly 50% of the female population?
  2. In Activity 12, you identified the range (data bin) within which your own height is situated. Use this range to place the vertical lines at the lower and upper values of this range. Note down what percentage of both male and female populations would be in this same range.

Discussion

  1. Note that your own answers may vary slightly because the activity relies on a visual judgement to locate the lines. But your figures should be close to these.

    • a.For the male population the range is approximately 1.72–1.82 m (roughly 50% of the male population).
    • b.For the female population the range is approximately 1.57–1.67 m (roughly 50% of the female population).
  2. If you used the example of the height range 1.6–1.7 m (Activity 12), you would have found that roughly 49% (48.59%) of the female population and 16% (16.36%) of the male population is in this range.

By playing with this data visually, you have learned some useful things about the desk height problem. In particular, you may now be able to visualise just how exclusive some design decisions can be; the decision to use a particular height might exclude a whole section of a population from that product. The example answer given in Activity 14 (Question 2), demonstrated a sizeable population difference between male and female heights.

Clearly, seeing the world from a range of different users' perspectives can have a dramatic effect on the design process.

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