11. The following shows the age distribution in years of 40 youths at a youth rally.
Age in years (x)
Frequency (f)
7 − 12. 4
12 − 17
17 − 22. 15
22 − 27
27 − 32. 5
Total. 40
Given that the median age is 19.8 years:
i.
Find the missing frequencies to the nearest whole number.
ii.
Find the mode of this distribution.
iii.
How many youths are older than 17 years?
iv.
Include a column for relative frequencies.
v.
Hence, or otherwise, construct a pie chart for this data.
Given, Median=19.8
(i) Median "M=l+\\dfrac{(\\frac{N}{2}-cf)}{f}h"
"\\Rightarrow 19.8=17+\\dfrac{\\frac{40}{2}-(4+f_1)}{15}\\times 5"
"\\Rightarrow 2.8=\\dfrac{16-f_1}{3}\\Rightarrow f_1=16-8.4=7.6"
Also, "24+f_1+f_2=40"
"f_2=40-24-7.6=8.4"
Missing frequencies are 7.6 and 8.4
(ii) Mode "=l+\\dfrac{(f_m-f_{m-1})}{2f_m-f_{m-1}-f_{m+1}}h"
"=17+\\dfrac{15-7.6}{2\\times 15-7.6-8.4}\\times 5"
"=17+2.8=19.8"
(iii) Number of youths older than 17 years are "= 15+f_2+5=20+8.4=28.4"
(iv) Relative frequency table is included in the above chart.
(v) Pie chart for the given distribution is-
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