Scatter plots usually display the relation between two continuous variables plotted on the x and y axes. A one way scatter plot may be used to display a single continuous variable, but a disadvantage is that the plot may be difficult to read if too many points lie close together. Box plots display only a summary of the data, and some of the information about the shape of the distribution is obscured. For example, a box plot may extend from the 25th centile to the 75th centile and contain a line representing the median. Lines projecting out from the box may be added (“whiskers”) to display more extreme parts of the distribution of values. A histogram is perhaps the most commonly used graphical method of displaying either continuous data, such as height, or discreet data, such as mortality. The horizontal axis displays the limits that are used for each interval. For each interval a rectangular column centred on the midpoint is drawn rising from the horizontal axis. The vertical axis measures the number of values that fall within each interval or, if desired, the percentage of values that fall within each interval. Hypothesis testing is not a method for displaying data. |
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