Question

Draw a frequency polygon for the following data without using histogram.

Class interval	$10-20$	$20-30$	$30-40$	$40-50$	$50-60$	$60-70$	$70-80$	$80-90$
Frequency	$4$	$6$	$8$	$10$	$12$	$14$	$7$	$5$

Answer 1

Mark the class intervals along the X-axis and the frequency along the Y-axis. We take the imagined classe $0-10$ at the beginning and $90-100$ at the end, each with frequency zero. We have tabulated the data as shown. Using the adjacent table, plot the points A$(5,0)$, B$(15,4)$, C$(25,6)$, D$(35,8)$, E$(45,10)$, F$(55,12)$, G$(65,14)$, H$(75,7)$, I$(85,5)$ and J$(95,0)$.

Class interval	Midpoints	Frequency
$0-10$	$5$	$0$
$10-20$	$15$	$4$
$20-30$	$25$	$6$
$30-40$	$35$	$8$
$40-50$	$45$	$10$
$50-60$	$55$	$12$
$60-70$	$65$	$14$
$70-80$	$75$	$7$
$80-90$	$85$	$5$
$90-100$	$95$	$0$

We draw the line segments AB, BC, CD, DE,, EF, FG, GH, HI, IJ to obtain the required frequency polygon ABCDEFGHIJ, which is shown in Figure.