First, we construct a cumulative frequency table
Salary (in Rs.thousand)Number of persons(fi)Cumulative frequency(cf) 5−10 49=f149=(cf ) 10−15 fm=133=f133+49=182 15−20 63=f2182+63=245 20−25 15245+15=260 25−30 6260+6=266 30−35 7266+7=273 35−40 4273+4=277 40−45 2277+2=279 45−50 1279+1=280 N=280
∴N2=2802=140
(i) Here, median class is 10-15, because 140 lies in it.
Lower limit(l)=10, Frequency(f)=133,
Cumulative frequency cf=49 and class width(h)=5
∴Median=l+(N2−cf)f×h=10+(140−49)133×5=10+91×5133=10+455133=10+3.421=Rs.13.421(in thousand)=13.421×1000=Rs.13421
(ii) Here, the highest frequency is 133, which lies in the interval 10-15, called modal class.
Lower limit(l)=10, class width(h)=5, fm=133, f1=49 and f2=63.
∴Mode=l+(fm−f12fm−f1−f2×h)=10+{133−49(2×133)−49−63}×5=10+84×5266−112=10+84×5154=10+2.727=Rs.12.727(in thousand)=12.727×1000=Rs.12727
Hence, the median and modal salary are Rs. 13421 and Rs. 12727, respectively.