Book contents
- Frontmatter
- Contents
- Introduction
- How important is maths in data-handling?
- Abbreviations and the Système International
- Acknowledgements
- 1 Numbers and indices
- 2 A sense of proportion
- 3 Graphs
- 4 Algebra
- 5 Logarithms: exponential and logarithmic functions
- 6 Simple statistics
- 7 Preparing solutions and media
- 8 Enzymes
- 9 Spectrophotometry
- 10 Energy metabolism
- 11 Radioactivity
- 12 Growth in batch cultures
- 13 Growth in continuous culture
- 14 Microbial genetics
- 15 Problems
- 16 Advice and hints
- 17 Answers to problems
- Conclusion
- Further reading
- Index
3 - Graphs
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Introduction
- How important is maths in data-handling?
- Abbreviations and the Système International
- Acknowledgements
- 1 Numbers and indices
- 2 A sense of proportion
- 3 Graphs
- 4 Algebra
- 5 Logarithms: exponential and logarithmic functions
- 6 Simple statistics
- 7 Preparing solutions and media
- 8 Enzymes
- 9 Spectrophotometry
- 10 Energy metabolism
- 11 Radioactivity
- 12 Growth in batch cultures
- 13 Growth in continuous culture
- 14 Microbial genetics
- 15 Problems
- 16 Advice and hints
- 17 Answers to problems
- Conclusion
- Further reading
- Index
Summary
‘and what is the use of a book,’ thought Alice, ‘without pictures or conversation?’
Lewis CarrollWhy draw a graph? There are many reasons, but the fundamental one is that the human brain understands a picture much more easily than it does a table of numbers.
Many data-handling questions require a graph to be drawn as part of the solution. It is unlikely that under examination conditions a work of art will be produced, nor would one be expected. However, some marks are given for a graph that is correct (the points are plotted in the right places!) and which obeys the conventional rules.
As well as making the drawing, you will probably have to use the graph to read off some values, such as a gradient or an intercept or to measure test samples from an assay. Doing these interpretations will be considered after discussing how to produce a graph.
Drawing graphs
The graph shown in Fig. 3.1 illustrates a number of features.
There are several things to note. The horizontal scale (x axis, or abscissa) is given to the variable that is the more directly under the control of the investigator, and the variable that is measured for various values of x is plotted on the vertical scale (y axis, or ordinate). In Fig. 3.1, the times at which readings of the extinction are made are chosen by the experimenter, and so go on the x axis, while the extinctions themselves are less under control and follow from the selected times, and therefore go on the y axis.
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- Data-Handling in Biomedical Science , pp. 9 - 18Publisher: Cambridge University PressPrint publication year: 2010