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Statistics Test - 40

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Statistics Test - 40
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  • Question 1
    1 / -0
    Find the median of the following data

    Solution
     $$C.I$$ $$Frequency(f)$$ $$Cumulative\ Frequency$$ 
     $$0-10$$ $$5$$$$5$$
     $$10-20$$ $$8$$ $$13$$
     $$20-30$$ $$12$$$$25$$
     $$30-40$$$$14$$ $$39$$
     $$40-50$$ $$11$$$$50$$
       $$N = 50$$
    $$ \dfrac {N}{2} = \dfrac {50}{2} = 25 $$
    So, the median lies in the class $$ 20 - 30 $$
    Now,  median $$ =  { l }_{ 1 } +\left[ \dfrac { \dfrac { N }{ 2 } -cf }{ f }  \right] \times  h $$
    Where $${ l }_{ 1 } $$  lower limit of the median class
    $$ f = $$ frequency of the median class
    $$ h = $$ size of the median class
    $$ c = $$ cumulative  frequency of the class preceding the median class
    So, median $$ =  20 +\left[ \dfrac { \dfrac { 50 }{ 2 } -13 }{ 12 }  \right] \times \quad 10 =  30 $$. 
  • Question 2
    1 / -0
    Find the arithmetic mean of the following data.

    Solution
    $$mean= \dfrac{\sum x_{i}f_{i}}{\sum f_{i}}=\dfrac{(6\times 9)+(8\times 7)+(10\times 15)+(12\times 13)+(14\times 6)}{9+7+15+13+6}=\dfrac{54+56+150+156+84}{50}$$
    $$=\dfrac{500}{50}=10$$
  • Question 3
    1 / -0
    Find the median of the following data.
     $$x$$$$14$$ $$18$$ $$22$$ $$25$$ $$30$$ 
     $$f$$$$7$$ $$10$$ $$12$$ $$16$$ $$5$$ 
    Solution
     $$N = 50$$    So, Median $$\displaystyle =\frac{\left ( \frac{N}{2} \right )^{th}obs+\left ( \frac{N}{2}+1 \right )^{th}obs}{2}$$
    $$\displaystyle =\frac{25^{th}obs+26^{th}obs}{2}=\frac{22+22}{2}=22$$
    Hence, the answer is $$22$$.
  • Question 4
    1 / -0
    Find the mode of 0,0,2,2,3,3,3,4,5,5,5,5,6,6,7,8
    Solution
    $$Number$$                     $$Frequency$$
             0                                     2
             2                                     2
             3                                     3
             4                                     1   
             5                                     4 
             6                                     2
             7                                      1
             8                                      1
     
    Frequency of 5 is maximum. Hence 5 is the mode.         
  • Question 5
    1 / -0
    Find the median of the following data

    Solution
     Class Interval Frequency $$(f)$$ Cumulative Frequency
     $$0-20$$ $$18$$$$ 8$$
     $$20-40$$ $$10$$$$18$$
     $$40-60$$ $$ 12$$$$ 30$$
     $$ 60-80$$ $$9$$$$39$$
     $$80-100$$ $$9$$$$48$$
       $$N = 48$$
    From table, we have
    $$ \dfrac {N}{2} = \dfrac {48}{2} = 24 $$

    So, the median lies in the class $$ 40 - 60 $$.

    Now,  median $$ =  { l }_{ 1 } +\left[ \dfrac { \dfrac { N }{ 2 } -cf }{ f }  \right] \times  h $$
    Where $${ l }_{ 1 } =$$ lower limit of the median class
    $$ f = $$ frequency of the median class
    $$ h = $$ size of the median class
    $$ c = $$ cumulative  frequency of the class preceding the median class

    So, median $$ =  40 +\left[ \dfrac { \dfrac { 48 }{ 2 } -18 }{ 12 }  \right] \times 20 $$
    $$=40 + \left[ \dfrac{24-18}{12} \right] \times 20$$
    $$=40+\left (\dfrac{1}{2} \times 20 \right)$$
    $$=  50 $$
  • Question 6
    1 / -0
     C.I. 0-4 4-8 8-12 12-1616-20 
     f 5 6 19 12 8
    Find the mode of the following data:
    Solution
     CI Frequency(f)
     0-4 5
     4-8 6
     8-12 19
     12-1612
    16-20 8
      
    Since the class $$ 8 - 12 $$ has the highest frequency, therefore, it is the modal class
    Now,  Mode $$ = l+\dfrac { { f }_{ 1 }-{ f }_{ 0 } }{ 2{ f }_{ 1 }-{ f }_{ 0 }-{ f }_{ 2 } } \times h $$
    Where $$ l $$  lower limit of the modal class
    $$ {f}_{1} = $$ frequency of the modal class
    $$ {f}_{0} = $$ frequency of the class preceeding the modal class
    $$ {f}_{2} = $$ frequency of the class succeeding the modal class
    $$ h = $$ size of the class interval
    So, Mode $$ = 8+\dfrac { 19-6 }{ 2(19)-6-12 } \times 4 = 10.6 $$. 
  • Question 7
    1 / -0
     Students 2 10 15 20 25
     Marks 100 90 75 80 85
    Find the mean for the following data 
    Solution
     Students
           $$xi$$
    $$\sum Marks$$
            $$fi$$
     $$\sum fixi$$
     2100 200 
     10 90 900
     15 75 1125
     20 80 1600
     25 85 2125
      $$\sum fi=430$$ $$\sum fixi=5950$$
    Arithmetic mean using direct method $$\bar { x } =\dfrac { \sum { { f }_{ i } } { x }_{ i } }{ \sum { { f }_{ i } }  } $$
    Mean, $$\bar { x } =\dfrac { 5,950 }{ 430 } $$
    $$\bar { x } =13.837$$.
  • Question 8
    1 / -0
    If the average of the following data is $$200.5$$, find the value of $$k$$ 

    Solution
    Answer:- Given:- $$\overline {x}=200.5$$
    Using frequency distribution table

     x f xf
     42
     12 8 96
     18 9 162
     24 k 24k
     30 5 150
     36 4 144
      $$\Sigma f_i = 33+k$$ $$\Sigma x_i f_i = 594+24k$$
    Average = $$\cfrac{\Sigma fx}{\Sigma f}$$
    $$\Rightarrow \; \overline{x} = \cfrac{594+24k}{33+k}$$
    $$\Rightarrow \; 200.5=\cfrac{594+24k}{33+k}$$
    $$\Rightarrow \; 200.5(33+k) = 594+24k$$
    $$\Rightarrow \; 6616.5 + 200.5k = 594 + 24k$$
    $$\Rightarrow \; 200.5k-24k = 594 - 6616.5 $$
    $$\Rightarrow \; 176.5k = -6022.5$$
    $$\Rightarrow \; k=-\cfrac{6022.5}{176.5}$$
    $$\Rightarrow \; k=-34.12 $$ 
  • Question 9
    1 / -0
    Find the average weight 

    Solution
    Answer:- Using direct method

    $$x_i$$ No. of persons
    $$f_i$$
    $$f_i x_i$$ 
    70 210 
     72 2144 
    80 180 
     90 4360 
     100 5 500
     $$\Sigma f_i = 15$$ $$\Sigma f_i x_i =1294$$ 
    Average = $$\cfrac { \Sigma f_{ i }x_{ i } }{ \Sigma f_{ i } } =\cfrac { 1294 }{ 15 } =86.26kg$$
  • Question 10
    1 / -0
    Find arithmetic mean for the table given below 

    Solution
    Arithmetic mean using direct method formula is $$\bar { x } =\dfrac { \sum { { f }_{ i } } { x }_{ i } }{ \sum { { f }_{ i } }  } $$
    First form a tabular column:
    Therefore, $$\bar { x } =\dfrac { \sum { { f }_{ i } } { x }_{ i } }{ \sum { { f }_{ i } }  } $$
    $$= \dfrac{114}{10}$$
    $$= 11.4$$

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