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Measures of Central Tendency Test - 26

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Measures of Central Tendency Test - 26
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  • Question 1
    1 / -0
    The mean of the following distribution is
    class
    Frequency
    0-5
    4
    5-10
    5
    10-15
    7
    15-20
    12
    20-25
    7
    25-30
    5

    Solution
    Mean $$=$$ $$\dfrac{sum \ of \ (Class mark \times frequency)}{Sum \ of \ frequency}$$

    Mean $$=$$ $$\dfrac{2.5\times 4 + 7.5\times5 + 12.5\times 7+ 17.5\times12 + 22.5\times 7 + 27.5\times 5}{4 +5+7+12+7 +5}$$
    Mean = $$\dfrac{640}{40} = 16$$
  • Question 2
    1 / -0
    The numbers $$ 4, 6\  and\  8$$  are the frequencies of $$(x +  2), x \ and\  (x - 1) $$ respectively . If their arithmetic mean is $$8,$$  the value of  $$x$$  is
    Solution
    $$8 =$$ $$\dfrac{4\times \left ( x+2 \right )+6x+8\times \left ( x-1 \right )} {4+6+8}$$
    $$=\dfrac{4x+8+6x+8x-8}{18}$$
    $$\therefore$$ $$x = 8$$
  • Question 3
    1 / -0
    The examination marks of $$250$$ pupils are recorded below. Find the mean.
    Class interval
    0-9
    10-19
    20-29
    30-39
    40-49
    Frequency
    0
    2
    6
    24
    36
    Class interval
    50-59
    60-69
    70-79
    80-89
    90-99
    Frequency
    47
    55
    40
    27
    13
    Solution
    $$Mean = \displaystyle \frac{Total  (mid  value  \times  frequency)}{Total frequency}$$
    Class interval
      Mid- value
     Fequency.  
    Mid-value $$\times$$ frequency
    0-9
     4.5
    0
    0
    10-19
    14.5
    2
    29
    20-29
    24.5
    6
    147
    30-39
    34.5
    24
    828
    40-49
    44.5
    36
    1602
    50-59
    54.5
    47
    2561.5
    60-69
    64.5
    55
    3547.5
    70-79
    74.5
    40
    2980
    80-89
    84.5
    27
    2281.5
    99-99
    94.5
    13
    1228.5


    Total - 250
    Total 15205
    $$Mean = \displaystyle \frac{Total  (mid  value  \times  frequency)}{Total  frequenct} = \frac{15205}{250}= 60.82$$
  • Question 4
    1 / -0
    A contractor employed $$18$$  labourers at Rs. $$12$$ per day, $$ 10$$ labourers at Rs.$$ 13.50 $$ per  day,$$ 5$$ labourers at Rs.$$ 25 $$ per  day and $$2$$ labourers at Rs.$$ 42$$ per day. The average  wage of a labourer per day is 
    Solution
    Mean = $$\dfrac{Total Sum}{Total Count}$$

    Mean = $$\dfrac{18\times12 + 10\times13.50 + 5\times25 + 2\times42}{18+10+5+2}$$
    = $$\dfrac{560}{35}$$
    $$= 16$$
  • Question 5
    1 / -0
    In a class test in English $$10$$ students scored $$75$$ marks, $$12$$ students scored $$60$$ marks, $$8$$ scored $$40$$ marks and $$3$$ scored $$30$$ marks, the mode  for their score is
    Solution
    $$\textbf{Step -1: Defining mode.}$$
                      $$\text{In a given data set, the mode is the value that appears most often among every other values.}$$
                      $$\text{Given data set says, }$$
                      $$\text{10 Students scored 75 marks.}$$
                      $$\text{12 Students scored 60 marks.}$$
                      $$\text{8 Students scored 40 marks.}$$
                      $$\text{3 Students scored 30 marks.}$$
    $$\textbf{Step -2: Finding the mode of their score.}$$
                      $$\text{The mode of their score will be the marks occurring most often.}$$
                      $$\therefore \text{12 Students scored 60 marks.}$$
                      $$\text{Hence 60 is the mode of their score.}$$
    $$\textbf{Hence,The mode of their score is 60. (Option C)}$$
  • Question 6
    1 / -0
    The marks of $$20$$ students in a test were as follows:
    $$5, 6, 8, 9, 10, 11, 11, 12, 13, 13, 14, 14, 15, 15, 15, 16, 16, 18, 19, 20$$
    The median is
    Solution
    Here, $$n$$ $$=$$ $$20$$ which is an even number.
    $$\therefore$$ Median $$= \displaystyle \cfrac{\left ( \dfrac{n}{2} \right )^{th} \text{term} + \left ( \dfrac{n}{2}+1\right )^{th} \text{term}}{2}$$
    $$\therefore$$ Median $$= \displaystyle \cfrac{\left ( \dfrac{20}{2} \right )^{th} \text{term} + \left ( \dfrac{20}{2}+1\right )^{th} \text{term}}{2}$$
    $$\displaystyle =\cfrac{10^{th}\: \text{term} + 11^{th}\: \text{term}}{2}$$
    $$\displaystyle =\cfrac{13+14}{2}=13.5$$
  • Question 7
    1 / -0
    The median of variables 5, 8, 10, 13, 17, 21, 27, 30, 33, 42 is
    Solution

  • Question 8
    1 / -0
    Arithmetic mean for the given data is
    Marks
    No. of students
    0 - 10
    10 - 20
    20 - 30
    30 - 40
    40 - 50
    50 - 60
    5
    10
    25
    30
    20
    10

    Solution
    Mean $$=$$ $$\dfrac{\text {Sum of} (\text {class mark} \times \text {frequency})}{\text {Sum of frequency}}$$

    Mean $$=$$ $$\dfrac{5\times 5 + 15\times10 + 25\times 25+ 35\times30 + 45\times 20 + 55\times 10}{5 +10+25+30+20 +10}$$

    Mean $$=$$ $$\dfrac{3300}{100}$$ = $$33$$
  • Question 9
    1 / -0
    The average weight of $$10$$ men is decreased by $$ 3 \space kg$$  when one of them whose weight is $$80 kg $$  is replaced by a new person. The weight of the new person is
    Solution
    Let the mean of $$10$$ persons =$$ M$$
    Sum of weight of the persons $$ = 10M$$

    After replacing a person weighing 80 Kg with another weighing say$$ x$$ Kg, $$sum = 10M - 80 +x$$
    New Mean$$ = M-3$$
    hence,$$ 10(M-3) = 10M - 80 +x $$
    $$10M- 30= 10M -80 +x$$
    $$x = 50 Kg$$
  • Question 10
    1 / -0
    In a family, there are $$8$$ men, $$7$$ women and $$5$$ children whose mean ages separately are respectively $$24,20$$ and $$6$$ years. The mean age of the family is
    Solution
    Here we have three collections for which $${ A }_{ 1 }=24,{ n }_{ 1 }=8;{ A }_{ 2 }=20,{ n }_{ 2 }=7$$ and $${ A }_{ 3 }=6,{ n }_{ 3 }=5$$.
    Their combined mean is the required mean.
    By the formula $$\displaystyle A=\frac { { n }_{ 1 }{ A }_{ 1 }+{ n }_{ 2 }{ A }_{ 2 }+{ n }_{ 3 }{ A }_{ 3 } }{ { n }_{ 1 }+{ n }_{ 2 }+{ n }_{ 3 } } =\frac { 8\times 24+7\times 20+5\times 6 }{ 8+7+5 } $$
    $$\displaystyle =\frac { 192+140+30 }{ 20 } =\frac { 362 }{ 20 } =18.1$$
    $$\therefore$$ The mean age of the family $$=18.1$$ years
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