Statistics · JEE Main previous year questions

2018 4 questions

1. Q202018 · 16 Apr 2018 · Shift 1

   The mean and the standard deviation(s.d.) of five observations are9 and 0, respectively. If one of the observations is changed such that the mean of the new set of five observations becomes 10, then their s.d. is :

   1. A.0
   2. B.1
   3. C.2
   4. D.4
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   Answer: C

2. Q172018 · 15 Apr 2018 · Shift 1

   In a triangle ABC, coordinates of A are (1, 2) and the equations of the medians through B and C are respectively, $x+y=5$ and $x=4$. Then area of $\Delta \text{ ABC}$ (in sq. units) is :

   1. A.12
   2. B.4
   3. C.5
   4. D.9
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   Answer: D

3. Q202018 · 15 Apr 2018 · Shift 1

   The mean of set of 30 observations is 75. If each observation is multiplied by a non-zero number $\lambda$ and then each of them is decreased by 25, their mean remains the same. Then $\lambda$ is equal to :

   1. A.$\frac{1}{3}$
   2. B.$\frac{2}{3}$
   3. C.$\frac{4}{3}$
   4. D.$\frac{10}{3}$
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   Answer: C

4. Q172018 · 8 Apr 2018 · Shift 1

   If ${\sum }_{i=1}^9(x_i-5)=9$ and ${\sum }_{i=1}^9(x_i-5{)}^2=45$, then the standard deviation of the 9 items $x_1,x_2,\dots \dots \dots ,x_9$ is

   1. A.$3$
   2. B.$9$
   3. C.$4$
   4. D.$2$
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   Answer: D