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Statistics Test - 44
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  • Question 1
    1 / -0
    Find the Arithmetic mean of the above data 

    Solution
    By direct method:
    Marks Obtained
    ($$x_i$$) 
    No. of students
    ($$f_i$$) 
    $$f_i x_i$$ 
    $$50$$ $$3$$ $$150$$ 
     $$60$$ $$7$$ $$420$$
     $$70$$ $$5$$ $$350$$
     $$80$$ $$2$$$$160$$
    $$90$$  $$10$$ $$900$$
    $$100$$  $$2$$ $$200$$
     $$\sum f_i = 29$$ $$\sum f_i x_i = 2180$$ 
    $$\overline x=\cfrac{\sum f_i x_i}{\sum f_i} $$

        $$= \cfrac{2180}{29}$$

        $$ = 75.17$$
  • Question 2
    1 / -0
    Identify the model class for the following data$$:$$
    $$x$$$$1-2$$
    $$2-3$$
    $$3-4$$
    $$4-5$$
    $$5-6$$
    $$f$$$$0$$
    $$4$$
    $$3$$
    $$2$$
    $$1$$
    Solution
    Modal class is one, which has the highest frequency.

    The highest frequency is $$4$$ which is associated with the class $$2-3$$
    Therefore, the modal class is $$2-3$$.
  • Question 3
    1 / -0
    A college teacher has the following absentee record of $$50$$ students of a class for the whole year. Find the median.
    Number of days
    $$0-4$$
    $$4-8$$
    $$8-12$$
    $$12-16$$
    $$16-20$$
    Number of students
    $$10$$
    $$18$$
    $$9$$
    $$1$$
    $$12$$

  • Question 4
    1 / -0
    Find the median for the following data shows that distance covered by $$200$$ people to perform their IT project.
    Distance(km)
    $$5-15$$
    $$15-25$$
    $$25-35$$
    $$35-45$$
    Number of people
    $$60$$
    $$40$$
    $$80$$
    $$20$$

    Solution
    Distance(km)
    Number of people (f)
    Cumulative frequency (cf) 
    $$5-15$$
    $$60$$
    $$60$$
    $$15-25$$
    $$40$$
    $$60+40=100$$
    $$25-35$$
    $$80$$
    $$100+80=180$$
    $$35-45$$
    $$20$$
    $$180+20=200$$

    $$n=\Sigma f=200$$
    $$\displaystyle\frac{n}{2}=\frac{200}{2}=100$$

    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$n=\Sigma f=$$ Total number of frequency $$=200$$
    $$\displaystyle\frac{n}{2}=\frac{200}{2}=100$$
    So, the median class is $$25-35$$
    L$$=$$ Lower limit of the median class $$=25$$
    cf$$=$$ Cumulative frequency of the class preceding the median class $$=180$$
    f$$=$$ Frequency of the median class $$=80$$
    h$$=$$ class width$$=10$$
    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$=25+\left(\displaystyle\frac{\displaystyle\frac{200}{2}-180}{10}\right)\times 10$$
    $$=14+\left(\displaystyle\frac{100-180}{80}\right)\times 10$$
    $$=25-10$$
    $$=15$$
    Hence, the median is $$15$$km.

  • Question 5
    1 / -0
    Calculate the median of the farm size for the following data$$:$$
    Farm size
    $$2-5$$
    $$5-8$$
    $$8-11$$
    $$11-14$$
    $$14-17$$
    Rooms
    $$4$$
    $$8$$
    $$12$$
    $$16$$
    $$20$$

    Solution
    Farm size
    Frequencies(f)
    Cumulative frequency(cf)
    $$2-5
    $$4$$
    $$4$$
    $$5-8$$
    $$8$$
    $$4+8=12$$
    $$8-11$$
    $$12$$
    $$12+12=24$$
    $$11-14$$
    $$16$$
    $$24+16=40$$
    $$14-17$$
    $$20$$
    $$40+20=60$$

    $$n=\Sigma f=60$$
    $$\displaystyle\frac{n}{2}=\frac{60}{2}=30$$

    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$n=\Sigma f=$$ Total number of frequency $$=60$$
    $$\displaystyle\frac{n}{2}=\frac{60}{2}=30$$
    So, the median class is $$11-14$$
    L$$=$$ Lower limit of the median class $$=11$$
    cf$$=$$ Cumulative frequency of the class preceding the median class $$=40$$
    f$$=$$ Frequency of the median class $$=16$$
    h$$=$$ class width$$=3$$
    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$=11+\left(\displaystyle\frac{\displaystyle\frac{60}{2}-40}{16}\right)\times 3$$
    $$=11+\left(\displaystyle\frac{30-40}{16}\right)\times 3$$
    $$=11-1.875$$
    $$=9.125$$
    Hence, the median is $$9.125$$

  • Question 6
    1 / -0
    Identify the modal class for the following data $$:$$
    Farm
    $$20-30$$
    $$30-40$$
    $$40-50$$
    $$50-60$$
    $$60-70$$
    Animals
    $$12$$
    $$14$$
    $$21$$
    $$34$$
    $$15$$

    Solution
    Modal class is the class which has the highest frequency.
    The highest frequency in the given data is $$34$$ which is associated with the class $$50-60$$.
    Therefore, the modal class is $$50-60$$.
    The answer is $$B$$
  • Question 7
    1 / -0
    The following frequency distribution showing the marks obtained by $$100$$ students in Maths. Find the median.
    Marks
    $$10-20$$
    $$20-30$$
    $$30-40$$
    $$40-50$$
    Frequency
    $$10$$
    $$15$$
    $$25$$
    $$50$$


    Solution
    Marks  
           Frequencies$$(f)$$       
    Cumulative frequency$$(cf)$$
    $$10-20$$   
           $$10$$
    $$0$$
    $$20-30$$     
           $$15$$
    $$10+15=25$$
    $$30-40$$ 
           $$25$$
    $$25+25=50$$
    $$40-50$$
           $$50$$
    $$50+50=100$$


    $$n=\Sigma f=100$$

    $$\displaystyle\frac{n}{2}=\frac{100}{2}=50$$


    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$n=\Sigma f=$$ Total number of frequency $$=100$$
               $$\displaystyle\frac{n}{2}=\frac{100}{2}=50$$
    So, the median class is $$40-50$$
     $$l=$$ Lower limit of the median class $$=40$$
    $$cf$$= Cumulative frequency of the class preceding the median class = $$50$$
    $$f=$$ Frequency of the median class $$=50$$
    $$h=$$ class width$$=10$$
    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$=40+\left(\displaystyle\frac{\displaystyle\frac{100}{2}-50}{50}\right)\times 10$$
    $$=40+\left(\displaystyle\frac{50-50}{50}\right)\times 10$$
    $$=40+0$$
    $$=40$$
    Hence, the median is $$40$$. (option $$A$$)
  • Question 8
    1 / -0
    Estimate the median for the following data$$:$$
    Daily wages
    $$22-24$$
    $$24-26$$
    $$26-28$$
    $$28-30$$
    $$30-32$$
    Number of workers
    $$23$$
    $$120$$
    $$100$$
    $$110$$
    $$105$$

    Solution
     Daily wages Number of workers(f)Cumulative frequency (cf)

     $$22-24$$ $$23$$$$23$$
     $$24-26$$ $$120$$ $$23+120=143$$
     $$26-28$$ $$100$$ $$143+100=243$$
     $$28-30$$ $$110$$
     $$243+110=353$$
    $$30-32$$
     $$105$$ $$353+105=458$$
       

    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$

    $$n=\Sigma f=$$ Total number of frequency $$=458$$

    $$\displaystyle\frac{n}{2}=\frac{458}{2}=229$$

    So, the median class is $$26-28$$

    L$$=$$ Lower limit of the median class $$=26$$

    cf$$=$$ Cumulative frequency of the class preceding the median class 

       $$=143$$

    f$$=$$ Frequency of the median class $$=100$$

    h$$=$$ class width$$=2$$

    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$

    $$=26+\left(\displaystyle\frac{\displaystyle\frac{458}{2}-143}{100}\right)\times 2$$

    $$=26+\left(\displaystyle\frac{229-143}{100}\right)\times 2$$

    $$=26+1.72$$

    $$=27.72$$

    Hence, the median is $$27.72$$.
  • Question 9
    1 / -0
    Calculate the median of income used by employee for the following data $$:$$
    Income
    $$4-14$$
    $$14-24$$
    $$24-34$$
    $$34-44$$
    Employee
    $$12$$
    $$10$$
    $$8$$
    $$4$$

    Solution
    Income
    Employees(f)
    Cumulative frequency (cf)
    $$4-14$$
    $$12$$
    $$12$$
    $$14-24$$
    $$10$$
    $$12+10=22$$
    $$24-34$$
    $$8$$
    $$22+8=30$$
    $$34-44$$
    $$4$$
    $$30+4=34$$

    $$n=\Sigma f=34$$
    $$\displaystyle\frac{n}{2}=\frac{34}{2}=17$$

    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$n=\Sigma f=$$ Total frequency $$=34$$
    $$\displaystyle\frac{n}{2}=\frac{12}{2}=17$$
    So, the median class is $$14-24$$
    L$$=$$ Lower limit of the median class $$=14$$
    cf$$=$$ Cumulative frequency of the class preceding the median class $$=12$$
    f$$=$$ Frequency of the median class $$=10$$
    h$$=$$ class width$$=10$$
    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$=14+\left(\displaystyle\frac{\displaystyle\frac{24}{2}-12}{10}\right)\times 10$$
    $$=14+\left(\displaystyle\frac{17-12}{10}\right)\times 10$$
    $$=14+5$$
    $$=19$$
    Hence, the median is $$19$$.



  • Question 10
    1 / -0
    Find the median for the grouped data given below$$:$$
    Marks
    $$50-60$$
    $$60-70$$
    $$70-80$$
    $$80-90$$
    Students
    $$3$$
    $$4$$
    $$8$$
    $$5$$
    Solution
    Marks
    Students(f)
    Cumulative frequency(cf)
    $$50-60$$
    $$3$$
    $$3$$
    $$60-70$$
    $$4$$
    $$3+4=7$$
    $$70-80$$
    $$8$$
    $$7+8=15$$
    $$80-90$$
    $$5$$
    $$15+5=20$$

    $$n=\Sigma f=20$$
    $$\displaystyle\frac{n}{2}=\frac{20}{2}=10$$

    Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$n=\Sigma f=$$ Total number of frequency $$=20$$
    $$\displaystyle\frac{n}{2}=\frac{20}{2}=10$$
    So, the median class is $$70-80$$
    L$$=$$ Lower limit of the median class $$=70$$
    cf$$=$$ Cumulative frequency of the class preceding the median class $$=15$$
    f$$=$$ Frequency of the median class $$=8$$
    h$$=$$ class width$$=10$$
    Therefore, Median $$=l+\left(\displaystyle\frac{\displaystyle\frac{n}{2}-cf}{f}\right)\times h$$
    $$=70+\left(\displaystyle\frac{\displaystyle\frac{20}{2}-15}{8}\right)\times 10$$
    $$=70+\left(\displaystyle\frac{10-15}{8}\right)\times 10$$
    $$=70-6.25$$
    $$=63.75$$
    Hence, the median is $$63.75$$
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