Age when girls menstruate
Use this diagram to introduce the idea of predicting the proportion menstruating from age.
Click Stacked. The proportion menstruating increases steadily with age.
Bar charts have been used to convey the ideas. However age is a numerical variable that has been grouped into classes whose widths are unequal, so histograms (and stacked histograms) would describe the data better. In particular, bar charts of the frequencies do not describe the distribution of ages well.
A study was conducted in Warsaw to determine the proportions of girls who had started menstruating at different ages. A total of 3898 girls of various ages between 8 and 19 were asked whether they had started menstruating.
Age class (to nearest month) | Menstruating | Total girls | |||
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