\n185 – 205<\/td>\n | 4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Solution: \n<\/strong>We may find class marks by using the relation<\/p>\n\n \nTaking 135 as assumed mean (a) we may find di<\/sub>, ui<\/sub>, fi<\/sub>ui<\/sub>, according to step deviation method as following<\/p>\n\n\n\nMonthly consumption\u00a0<\/strong> \n(in units)<\/strong><\/td>\nNumber of consumers (f\u00a0i<\/sub><\/em>)<\/strong><\/td>\nxi<\/sub><\/em><\/strong>\u00a0class mark<\/strong><\/td>\ndi<\/sub>\u00a0<\/em><\/strong>=\u00a0xi<\/sub>\u00a0<\/em>– 135<\/strong><\/td>\n <\/strong><\/td>\nfi<\/sub>ui<\/sub>\u00a0<\/strong><\/td>\n<\/tr>\n\n65 – 85<\/td>\n | 4<\/td>\n | 75<\/td>\n | – 60<\/td>\n | – 3<\/td>\n | – 12<\/td>\n<\/tr>\n | \n85 – 105<\/td>\n | 5<\/td>\n | 95<\/td>\n | – 40<\/td>\n | – 2<\/td>\n | – 10<\/td>\n<\/tr>\n | \n105 – 125<\/td>\n | 13<\/td>\n | 115<\/td>\n | – 20<\/td>\n | – 1<\/td>\n | – 13<\/td>\n<\/tr>\n | \n125 – 145<\/td>\n | 20<\/td>\n | 135<\/td>\n | 0<\/td>\n | 0<\/td>\n | 0<\/td>\n<\/tr>\n | \n145 – 165<\/td>\n | 14<\/td>\n | 155<\/td>\n | 20<\/td>\n | 1<\/td>\n | 14<\/td>\n<\/tr>\n | \n165 – 185<\/td>\n | 8<\/td>\n | 175<\/td>\n | 40<\/td>\n | 2<\/td>\n | 16<\/td>\n<\/tr>\n | \n185 – 205<\/td>\n | 4<\/td>\n | 195<\/td>\n | 60<\/td>\n | 3<\/td>\n | 12<\/td>\n<\/tr>\n | \nTotal<\/td>\n | 68<\/td>\n | <\/td>\n | <\/td>\n | <\/td>\n | 7<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n From the table we may observe that<\/p>\n <\/p>\n Now from table it is clear that maximum class frequency is 20 belonging to class interval 125 – 145. \nModal class = 125 – 145 \nLower limit (l) of modal class = 125 \nClass size (h) = 20 \nFrequency (f1<\/sub>) of modal class = 20 \nFrequency (f0<\/sub>) of class preceding modal class = 13 \nFrequency (f2<\/sub>) of class succeeding the modal class = 14<\/p>\n \nWe know that \n3 median = mode + 2 mean \n= 135.76 + 2 (137.058) \n= 135.76 + 274.116 \n= 409.876 \nMedian = 136.625 \nSo median, mode, mean of given data is 136.625, 135.76, 137.05 respectively.<\/p>\n
Question 2. \n<\/strong>If the median of the distribution is given below is 28.5, find the values of x and y.<\/p>\n\n\n\nClass interval<\/strong><\/td>\nFrequency<\/strong><\/td>\n<\/tr>\n\n0 – 10<\/td>\n | 5<\/td>\n<\/tr>\n | \n10 – 20<\/td>\n | x<\/em><\/td>\n<\/tr>\n\n20 – 30<\/td>\n | 20<\/td>\n<\/tr>\n | \n30 – 40<\/td>\n | 15<\/td>\n<\/tr>\n | \n40 – 50<\/td>\n | y<\/em><\/td>\n<\/tr>\n\n50 – 60<\/td>\n | 5<\/td>\n<\/tr>\n | \nTotal<\/td>\n | 60<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Solution:<\/strong> \nWe may find cumulative frequency for the given data as following<\/p>\n\n \n\n\nClass interval<\/strong><\/td>\nFrequency<\/strong><\/td>\nCumulative frequency\u00a0<\/strong><\/td>\n<\/tr>\n\n0 – 10<\/td>\n | 5<\/td>\n | 5<\/td>\n<\/tr>\n | \n10 – 20<\/td>\n | x<\/em><\/td>\n5\u00a0<\/em>+\u00a0x<\/em><\/td>\n<\/tr>\n\n20 – 30<\/td>\n | 20<\/td>\n | 25 +\u00a0x<\/em><\/td>\n<\/tr>\n\n30 – 40<\/td>\n | 15<\/td>\n | 40 +\u00a0x<\/em><\/td>\n<\/tr>\n\n40 – 5<\/td>\n | y<\/em><\/td>\n40\u00a0<\/em>+\u00a0x\u00a0<\/em>+\u00a0y<\/em><\/td>\n<\/tr>\n\n50 – 60<\/td>\n | 5<\/td>\n | 45 +\u00a0x<\/em>\u00a0+\u00a0y<\/em><\/td>\n<\/tr>\n\nTotal (n<\/em>)<\/td>\n60<\/td>\n | <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n It is clear that n = 60<\/p>\n 45 + x + y = 60<\/p>\n x + y = 15\u00a0\u00a0 \u00a0\u00a0\u00a0 \u00a0(1) \nMedian of data is given as 28.5 which lies in interval 20 – 30. \nSo, median class = 20 – 30 \nLower limit (l) of median class = 20 \nCumulative frequency (cf) of class preceding the median class = 5 + x \nFrequency (f) of median class = 20 \nClass size (h) = 10 \n \nFrom equation (1) \n8 + y = 15 \ny = 7 \nHence values of x and y are 8 and 7 respectively.<\/p>\n Question 3<\/strong><\/p>\nA life insurance agent found the following data for distribution of ages of 100 policy holders. Calculate the median age, if policies are given only to persons having age 18 years onwards but less than 60 year.<\/p>\n \n\n\nAge (in years)<\/strong><\/td>\nNumber of policy holders<\/strong><\/td>\n<\/tr>\n\nBelow 20<\/td>\n | 2<\/td>\n<\/tr>\n | \nBelow 25<\/td>\n | 6<\/td>\n<\/tr>\n | \nBelow 30<\/td>\n | 24<\/td>\n<\/tr>\n | \nBelow 35<\/td>\n | 45<\/td>\n<\/tr>\n | \nBelow 40<\/td>\n | 78<\/td>\n<\/tr>\n | \nBelow 45<\/td>\n | 89<\/td>\n<\/tr>\n | \nBelow 50<\/td>\n | 92<\/td>\n<\/tr>\n | \nBelow 55<\/td>\n | 98<\/td>\n<\/tr>\n | \nBelow 60<\/td>\n | 100<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Solution: \n<\/strong>Here class width is not same. There is no need to adjust the frequencies according to class intervals. Now given frequency table is of less than type represented with upper class limits. As policies were given only to persons having age 18 years onwards but less than 60 years, we can define class intervals with their respective cumulative frequency as below<\/p>\n\n \n\n\nAge (in years)<\/strong><\/td>\nNumber of policy holders (fi<\/sub><\/em>)<\/strong><\/td>\nCumulative frequency (cf<\/em>)<\/strong><\/td>\n<\/tr>\n\n18 – 20<\/td>\n | 2<\/td>\n | 2<\/td>\n<\/tr>\n | \n20 – 25<\/td>\n | 6 – 2 = 4<\/td>\n | 6<\/td>\n<\/tr>\n | \n25 – 30<\/td>\n | 24 – 6 = 18<\/td>\n | 24<\/td>\n<\/tr>\n | \n30 – 35<\/td>\n | 45 – 24 = 21<\/td>\n | 45<\/td>\n<\/tr>\n | \n35 – 40<\/td>\n | 78 – 45 = 33<\/td>\n | 78<\/td>\n<\/tr>\n | \n40 – 45<\/td>\n | 89 – 78 = 11<\/td>\n | 89<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n45 – 50<\/td>\n | 92 – 89 = 3<\/td>\n | 92<\/td>\n<\/tr>\n | \n50 – 55<\/td>\n | 98 – 92 = 6<\/td>\n | 98<\/td>\n<\/tr>\n | \n55 – 60<\/td>\n | 100 – 98 = 2<\/td>\n | 100<\/td>\n<\/tr>\n | \nTotal (n<\/em>)<\/td>\n<\/td>\n | <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Now from table we may observe that\u00a0n<\/em>\u00a0= 100.<\/p>\nCumulative frequency (cf<\/em>) just greater than \u00a0is 78 belonging to interval 35 – 40 \nSo, median class = 35 – 40 \nLower limit (l) of median class = 35 \nClass size (h) = 5 \nFrequency (f) of median class = 33 \nCumulative frequency (cf) of class preceding median class = 45<\/p>\n \nSo, median age is 35.76 years.<\/p>\n
Question 4.<\/strong><\/p>\nThe lengths of 40 leaves of a plant are measured correct to the nearest millimeter, and the data obtained is represented in the following table:<\/p>\n \n\n\nLength (in mm)<\/strong><\/td>\nNumber or leaves\u00a0fi<\/sub><\/em><\/strong><\/td>\n<\/tr>\n\n118 – 126<\/td>\n | 3<\/td>\n<\/tr>\n | \n127 – 135<\/td>\n | 5<\/td>\n<\/tr>\n | \n136 – 144<\/td>\n | 9<\/td>\n<\/tr>\n | \n145 – 153<\/td>\n | 12<\/td>\n<\/tr>\n | \n154 – 162<\/td>\n | 5<\/td>\n<\/tr>\n | \n163 – 171<\/td>\n | 4<\/td>\n<\/tr>\n | \n172 – 180<\/td>\n | 2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Find the median length of the leaves. \n(Hint: The data needs to be converted to continuous classes for finding the median, since the formula assumes continuous classes. The classes then change to 117.5 – 126.5, 126.5 – 135.5 – 171.5 – 180.5) \nSolution:<\/strong><\/p>\n\n The given data is not having continuous class intervals. We can observe that difference between two class intervals is 1. So, we have to add and subtract 1\/2=0.5\u00a0 to upper class limits and lower class limits. \nNow continuous class intervals with respective cumulative frequencies can be represented as below<\/p>\n \n\n\nLength (in mm)<\/strong><\/td>\nNumber or leaves\u00a0fi<\/sub><\/em><\/strong><\/td>\nCumulative frequency<\/strong><\/td>\n<\/tr>\n\n117.5 – 126.5<\/td>\n | 3<\/td>\n | 3<\/td>\n<\/tr>\n | \n126.5 – 135.5<\/td>\n | 5<\/td>\n | 3 + 5 = 8<\/td>\n<\/tr>\n | \n135.5 – 144.5<\/td>\n | 9<\/td>\n | 8 + 9 = 17<\/td>\n<\/tr>\n | \n144.5 – 153.5<\/td>\n | 12<\/td>\n | 17 + 12 = 29<\/td>\n<\/tr>\n | \n153.5 – 162.5<\/td>\n | 5<\/td>\n | 29 + 5 = 34<\/td>\n<\/tr>\n | \n162.5 – 171.5<\/td>\n | 4<\/td>\n | 34 + 4 = 38<\/td>\n<\/tr>\n | \n171.5 – 180.5<\/td>\n | 2<\/td>\n | 38 + 2 = 40<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n From the table we may observe that cumulative frequency just greater then \u00a0 is 29, belonging to class interval 144.5 – 153.5. \nMedian class = 144.5 – 153.5 \nLower limit (l) of median class = 144.5 \nClass size (h) = 9 \nFrequency (f) of median class = 12 \nCumulative frequency (cf) of class preceding median class = 17 \n \nSo, median length of leaves is 146.75 mm.<\/p>\n Question 5. \n<\/strong>Find the following tables gives the distribution of the life time of 400 neon lamps:<\/p>\n\n\n\nLife time (in hours)<\/strong><\/td>\nNumber of lamps<\/strong><\/td>\n<\/tr>\n\n1500 – 2000<\/td>\n | 14<\/td>\n<\/tr>\n | \n2000 – 2500<\/td>\n | 56<\/td>\n<\/tr>\n | \n2500 – 3000<\/td>\n | 60<\/td>\n<\/tr>\n | \n3000 – 3500<\/td>\n | 86<\/td>\n<\/tr>\n | \n3500 – 4000<\/td>\n | 74<\/td>\n<\/tr>\n | \n4000 – 4500<\/td>\n | 62<\/td>\n<\/tr>\n | \n4500 – 5000<\/td>\n | 48<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Find the median life time of a lamp. \nSolution: \n<\/strong>We can find cumulative frequencies with their respective class intervals as below –<\/p>\n\n \n\n\nLife time<\/strong><\/td>\nNumber of lamps (fi<\/sub><\/em>)<\/strong><\/td>\nCumulative frequency<\/strong><\/td>\n<\/tr>\n\n1500 – 2000<\/td>\n | 14<\/td>\n | 14<\/td>\n<\/tr>\n | \n2000 – 2500<\/td>\n | 56<\/td>\n | 14 + 56 = 70<\/td>\n<\/tr>\n | \n2500 – 3000<\/td>\n | 60<\/td>\n | 70 + 60 = 130<\/td>\n<\/tr>\n | \n3000 – 3500<\/td>\n | 86<\/td>\n | 130 + 86 = 216<\/td>\n<\/tr>\n | \n3500 – 4000<\/td>\n | 74<\/td>\n | 216 + 74 = 290<\/td>\n<\/tr>\n | \n4000 – 4500<\/td>\n | 62<\/td>\n | 290 + 62 = 352<\/td>\n<\/tr>\n | \n4500 – 5000<\/td>\n | 48<\/td>\n | 352 + 48 = 400<\/td>\n<\/tr>\n | \nTotal (n<\/em>)<\/td>\n400<\/td>\n | <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Now we may observe that cumulative frequency just greater than \u00a0is 216 belonging to class interval 3000 – 3500. \nMedian class = 3000 – 3500 \nLower limit (l) of median class = 3000 \nFrequency (f) of median class = 86 \nCumulative frequency (cf) of class preceding median class = 130 \nClass size (h) = 500<\/p>\n \nSo, median life time of lamps is 3406.98 hours.<\/p>\n
Question 6. \n<\/strong>100 surnames were randomly picked up from a local telephone directory and the frequency distribution of the number of letters in the English alphabets in the surnames was obtained as follows:<\/p>\n\n\n\nNumber of letters<\/strong><\/td>\n1 – 4<\/td>\n | 4 – 7<\/td>\n | 7 – 10<\/td>\n | 10 – 13<\/td>\n | 13 – 16<\/td>\n | 16 – 19<\/td>\n<\/tr>\n | \nNumber of surnames<\/strong><\/td>\n | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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