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ALL ABOUT GRAPHS : OTHER TYPES OF GRAPHICAL REPRESENTATION Line graphs or curves represent the most commonly used type of graphical analysis but there are others.
SCATTERGRAMS
The relationship between oestradiol and testosterone levels during the menstrual cycle |
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| These graphs are useful in trying to determine the relationship between two variables, as in the example above, the relationship between testosterone and oestradiol in women. These data are not necessarily the result of controlled experimental work but data from surveys or field observations can be used. If the relationship is linear (the points follow roughly a straight line) then
the line of best fit or trend line can be drawn on the graph. The distance or spread of the points either side of this line indicates how close the two variables are related to one another (correlated). If the line rise to the right then there is said to be a positive correlation as in the case of this example. |
| If the line runs in the opposite direction, as shown below, then we say that there is a negative correlation between these variables |
The relationship between water temperature and the density of the flatworm Crenobia alpina in a stream, the Cotswolds G.B. |
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© Paul Billiet 2004 |
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