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12th Grade > Mathematics

STATISTICS AND COLLECTION OF STATISTICAL DATA MCQs

Statistics, Introduction To Statistics, Collection Of Data (11th And 12th Grade)

Total Questions : 105 | Page 8 of 11 pages
Question 71. The mean weight per student in a group of seven students is 55 kg if the individual weights of 6 students are 52, 58, 55, 53, 56 and 54; then weight of the seventh student is
  1.    55 kg
  2.    60 kg
  3.    57 kg
  4.    50 kg
 Discuss Question
Answer: Option C. -> 57 kg
:
C
Total weight of 7 students is =55×7=385kg
Sum of weight of 6 students
=52+58+55+53+56+54=328kg
Weight of seventh student =385328=57kg.
Question 72. The coefficient of  variation of  a distribution is
  1.    100×s.dmean
  2.    100×means.d
  3.    100×variancemean
  4.    s.dmean
 Discuss Question
Answer: Option A. -> 100×s.dmean
:
A
C.V.isdefinedbyC.V=100×s.dmean
Question 73. Suppose a population A has 100 observations 101, 102,……200 and another population B has 100    observation 151, 152….., 250. If VA,VB  represent the variances of the two populations respectively, then VAVB is
  1.    49
  2.    23
  3.    1
  4.    94
 Discuss Question
Answer: Option C. -> 1
:
C
Population B observations are 151, 152, ….., 250
Let y, be these observations
Shifting the origin zi=yi50
The values of these observations are 100, 101, ….., 200.
VA=VB
( Variance is independent of shifting the origin).
Question 74. If the mean of the number 27+x,31+x,89+x,107+x,156+x is 82, then the mean of 130+x,126+x,68+x,50+x,1+x is
  1.    75
  2.    157
  3.    82
  4.    80
 Discuss Question
Answer: Option A. -> 75
:
A
Given,
82=(27+x)+(31+x)+(89+x)+(107+x)+(156+x)5
82×5=410+5x410410=5xx=0
Required mean is,
¯¯¯x=130+x+126+x+68+x+50+x+1+x5
¯¯¯x=375+5x5=375+05=3755=75.
Question 75. The mean and S.D. of the marks of 200 candidates were found to be 40 and 15 respectively. Later, it was discovered that a score of 40 was wrongly read as 50. The correct mean and S.D. respectively are
  1.    14.98, 39.95
  2.    39.95, 14.98
  3.    39.95, 224.5
  4.    None the these
 Discuss Question
Answer: Option B. -> 39.95, 14.98
:
B
Correctedx=40×20050+40=7990
Corrected¯¯¯x=7990200=39.95
x2=n[σ2+¯¯¯x2]=200[152+402]=365000
Correctx2=3650002500+1600=364100
Correctedσ=364100200(39.95)2
=(1820.51596)=224.5=14.98.
Question 76. The mean of a set of observation is ¯¯¯x .If each observation is divided by α α0, and then is increased by 10,
then the mean of the new set is
  1.    ¯¯¯xα
  2.    ¯¯¯x+10α
  3.    ¯¯¯x+10αα
  4.    α¯¯¯x+10
 Discuss Question
Answer: Option C. -> ¯¯¯x+10αα
:
C
Let x1,x2,xn be n observations.
Then¯¯¯x=1nxi
letyi=xiα+10
¯¯¯y=1nniyi
And,¯¯¯y=1n[(nixiα+10.n]
¯¯¯y=1α¯¯¯x+10
=¯¯¯x+10αα.
Question 77. If a variable takes the discrete values α+4,α72,α52,α3,α2,α+12,α12,α+5(α>0),then the median is
  1.    α−54
  2.    α−12
  3.    α−2
  4.    α+54
 Discuss Question
Answer: Option A. -> α−54
:
A
Arrange the data as: α72,α3,α52,α2,α12,α+12,α+4,α+5,
Median =a2+α122=2α522=α54
Question 78. If the median and mode of 4 observations is 4, 6 and the sum of squares of observations is 48.  Then 
standard deviation is
 
  1.    √2
  2.    4
  3.    √3
  4.    √5
 Discuss Question
Answer: Option C. -> √3
:
C
Given that median = 4 and mode = 6. We know that
Mean - mode = 3 (Mean - Median)
Mean - 6 = 3 (Mean - 4)
¯x6=3¯x12
¯x=3
σ2=x2in(xin)2=484(3)2=3 σ=3
Question 79. If the algebraic sum of deviations of 20 observations from 30 is 20, then the mean of observations is
  1.    30
  2.    30.1
  3.    29
  4.    31
 Discuss Question
Answer: Option D. -> 31
:
D
20i=1(xi30)=20=20i=1xi20×30=20
20i=1xi=620.Mean=20i=120=62020=31.
Question 80.  If the mean of the set of number x1,x2...xn is ¯x ,then the mean of the number xi+2i,1n is 
  1.    ¯x+2n
  2.    ¯x+n+1
  3.    ¯x+2
  4.    ¯x+n
 Discuss Question
Answer: Option B. -> ¯x+n+1
:
B
¯x=ni=1xinni=1xi=n¯xni(xi+2i)n=ni=1xi+2(1+2+...+n)n=n¯x+2n(n+1)2n=¯x+(n+1)

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