WJEC Maths for AS: Applied sample

19 2.1 Interpreting diagrams for single variable data Here is a bar of a histogram. The height is the frequency density and the width is the class width and the area of the bar represents the frequency. Frequency density Class width Area of bar = frequency density × class width represents the frequency As frequency (area of bar) = frequency density × class width To work out frequency density we use: Frequency density = frequency class width The lengths of metal bars ( l  ) in m and their frequencies were recorded in the following table: Length ( l m) Class width (m) Frequency Frequency density 1.0 ≤ l < 1.2 0.2 4 20 1.2 ≤ l < 1.4 0.2 8 40 1.4 ≤ l < 1.8 0.4 12 30 1.8 ≤ l < 2.4 0.6 24 40 2.4 ≤ l < 2.6 0.2 14 70 2.6 ≤ l < 3.6 1.0 12 12 The data from the table can now be used to draw the following histogram: 70 60 50 40 30 20 10 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 Length (m) Frequency density