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501.

The height (in cms) of 20 childre of class 9 is given, find the mean. `{:("Height(in cm)","Number of children"),(" "120," "2),(" "121," "4),(" "122," "3),(" "123," "2),(" "124," "5),(" "125," "4):}`

Answer» Correct Answer - 122.8 cm
502.

The range of a data is x, the median and the mode of the data is 7 each. If the number of observations is odd and all observations are integers, then find the least value of x `("tange "ne 0)`A. 1B. 2C. 3D. 4

Answer» Correct Answer - A
Median of the data and mode are 7 each and the number of observations is odd.
since 7 is the mode, 7 should appear at least two times, and as median is 7, it must be the middle one.
6, 7, 7, can be taken as observations.
`:.` Range `=7-6=1`
Hence, the correct option is (a).
503.

Life (in hour) of 10 bulbs from each of four different companies A, B, C and D are given below in the table. `{:(A,B,C,D),(120,700,950,530),(1600,502,330,650),(280,1430,1200,720),(420,625,500,550),(800,780,445,748),(770,335,1260,570),(270,224,375,635),(455,1124,1130,804),(150,473,185,500):}` By using the coefficient of range find which company has shown the best consistency in its quality?A. AB. BC. CD. D

Answer» Correct Answer - D
(i) Find the coefficient of range of A, B, C and D and compare.
(ii) `"Coefficient of range" = ("Maximum value - Minimum value")/("Maximum Value + Minimum value")`
(iii) Find the coefficient of range of A, B, C and D.
(iv) The least coefficient of range implies good performance.
504.

Calculate the mean deviation about the median of the following observation:(i) 22, 24, 30, 27, 29, 31, 25, 28, 41, 42(ii) 38, 70, 48, 34, 63, 42, 55, 44, 53, 47

Answer»

(i) 22, 24, 30, 27, 29, 31, 25, 28, 41, 42

To calculate the Median (M), let us arrange the numbers in ascending order.

Median is the middle number of all the observation.

22, 24, 25, 27, 28, 29, 30, 31, 41, 42

Here the Number of observations are Even then Median = (28 + 29)/2 = 28.5

Median = 28.5 and n = 10

By using the formula to calculate Mean Deviation,

MD = 1/n ∑ni=1|di|

xi|di| = |xi – 28.5|
226.5
244.5
301.5
271.5
290.5
312.5
253.5
280.5
4112.5
4213.5
Total47

MD = 1/n ∑ni=1|di|

= 1/10 × 47

= 4.7

∴ The Mean Deviation is 4.7.

(ii) 38, 70, 48, 34, 63, 42, 55, 44, 53, 47

To calculate the Median (M), let us arrange the numbers in ascending order.

Median is the middle number of all the observation.

34, 38, 43, 44, 47, 48, 53, 55, 63, 70

Here the Number of observations are Even then Median = (47 + 48)/2 = 47.5

Median = 47.5 and n = 10

By using the formula to calculate Mean Deviation,

MD = 1/n ∑ni=1|di|

xi|di| = |xi – 47.5|
389.5
7022.5
480.5
3413.5
6315.5
425.5
557.5
443.5
535.5
470.5
Total84

MD = 1/n ∑ni=1|di|

= 1/10 × 84

= 8.4

∴ The Mean Deviation is 8.4.

505.

If the sum of mode and mean of certain observations is 129 and the median of the observations is 63, then find mode and mean.

Answer» Correct Answer - 69
506.

If the mode of the observations 5, 4, 4, 3, 5, x, 3, 4, 3, 5, 4, 3 amd 5 is 3, then find the median of the observations.A. 3B. 4C. 5D. 3.5

Answer» Correct Answer - B
Given, Mode = 3
`therefore x = 3`
Now, arrange the given data in ascending order, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, `therefore "Median" = 4`
Hence, option (b) is correct.
507.

The mode of observations 2x + 3, 3x - 2, 4x + 3, x - 1, 3x - 1, 5x + 2 (x is a positive integer) can beA. 3B. 5C. 7D. 9

Answer» Correct Answer - C
Substitute x = 1.
508.

Which of the following is same as representative of the whole class ?A) Lower limit B) Length of the class C) Upper limit D) Midpoint

Answer»

Correct option is: D) Midpoint

Mid -point is the representative of the whole class.

Correct option is: D) Midpoint

509.

Calculate the mean deviation about the median of the following observation : 22, 24, 30, 27, 29, 31, 25, 28, 41, 42

Answer»

Given, Numbers of observations are given. 

To Find: Calculate the Mean Deviation. 

Formula Used: Mean Deviation = \(\frac{\Sigma d_i}{n}\) 

Explanation: Here, Observations 22, 24, 30, 27, 29, 31, 25, 28, 41, 42are Given.

Since, Median is the middle number of all the observation, 

So, To Find the Median, Arrange the numbers in Ascending order, we get 

22, 24, 25, 27, 28, 29, 30, 31, 41, 42 

Here the Number of observations are Even then the middle terms are 28 and 29 

Therefore, The Median = \(\frac{28+29}{2}\) = 28.5

Deviation |d| = |x-Median| 

And, The number of observations is 10. 

Now, The Mean Deviation is

Xi|di| = |xi-28.5|
226.5
244.5
301.5
271.5
290.5
312.5
253.5
280.5
4112.5
4313.5
Total Σdi 47

Hence, The Mean Deviation is 8.7

Mean Deviation = \(\frac{47}{10}\) = 4.7

510.

Find the mean of 32, 35, 36, 31 and 41.

Answer» `"Mean" = "sum of observations"/"no. of observations"`
`=(32+35+36+31+41)/(5)`
`=(175)/(5) = 35`
511.

The lower limit of the class 60 – 69 is A) 9 B) 64.5 C) 60 D) 69

Answer»

Correct option is (C) 60

The lower limit of the class 60–69 is 60.

Correct option is  C) 60

512.

The median of 21 observations is 18. If two observations 15 and 24 are included to the observations, then the median of the new series isA. 15B. 18C. 24D. 16

Answer» Correct Answer - B
Observe median after including new observations.
513.

x123456f89k1698The mean of the above data is 3.55 then k =A) 10 B) 12 C) 31 D) 41

Answer»

Correct option is: A) 10

514.

Mode from the following data isx510152025f71220164A) 5 B) 25 C) 15 D) 10

Answer»

Correct option is: C) 15

515.

Cumulative frequency are used in ………calculations. A) A.M. B) median C) range D) mode

Answer»

Correct option is: B) median

Cumulative frequency are used in the calculations for median.

Correct option is: B) median

516.

The A.M of a + 2, a, a – 2 is ………………. A) a + 2 B) a C) a – 2 D) 3a

Answer»

Correct option is: B) a

A.M (Algebraic men) = \(\frac {sum \, of \, observations}{Total \, number \, of\, observations}\)

\(\frac {(a+2)+ a + (a-2)}{3} = \frac {3a}3 =a\)

Hence, A.M. of a+2, a, a-2 is a.

Correct option is: B) a

517.

The median of the observations 6, 21, 9, 19, 15 and 13 is A) 13 B) 19 C) 15 D) 14

Answer»

Correct option is (D) 14

The ascending order of observations is 6, 9, 13, 15, 19, 21.

Number of observations is n = 6.

\(\therefore\) Median \(=\frac{3^{rd}\text{ observation}+4^{th}\text{ observation}}2\)

\(=\frac{13+15}2\)

\(=\frac{28}2=14\)

Correct option is  D) 14

518.

Which of the following is not a measure of central tendency ? A) Mean B) Range C) Mode D) Median

Answer»

Correct option is: B) Range

519.

The mid value of the class 10 – 19 is …………A) 24.5 B) 20.5 C) 23.5 D) 14.5

Answer»

Correct option is: D) 14.5

Mid value = \(\frac {Lower \,limit + upper \, limit}{2} \)

\(= \frac {10+19}2 = \frac {29}2 = 14.5\)

Correct option is: D) 14.5

520.

In a class, seven students got 90 marks each, the frequency of the observation 90 is _____.

Answer» Correct Answer - 7
521.

The marks obtained by 17 students in a mathematics test (out of 100) are given below:90, 79, 76, 82, 65, 96, 100, 91, 82, 100, 49, 46, 64, 48, 72, 66, 88.Find the range of the above data.

Answer»

Arrange the given data in ascending order

46, 48, 49, 64, 65, 66, 68, 72, 76, 79, 82, 82, 90, 91, 96, 100, 100

So from the data we know that

Minimum marks = 46 and Maximum marks = 100

We know that

Range of the given data = Maximum marks – Minimum marks = 100 – 46 = 54

Therefore, the range of the above data is 54.

522.

30 children were asked about the number of hours they watched TV programmes last week. The result are recorded as underCan we say that the number of children who watched TV for 10 or more hour in a week is 22? Justify your answer.

Answer»

No, infact the number of children who watched TV for 10 or more hour in a week is 4 + 2 i.e.,6.

523.

Find the class mark of the class 90-120.

Answer»

Class of the class 90-120 = (Upper limit + Lower limit) / 2

So we get

Class of the class 90-120 = (90 + 120)/2 = 105

524.

The class marks of a continuous distribution are 1.04, 1.14, 1.24, 1.34, 1.44,1.54 and 1.64.Is it correct to say the last interval will be 1.55-1.73? Justify your answer.

Answer»

It is not correct. Because the difference between two consecutive class marks should be equal to the class size. Here, difference between two consecutive marks is 0.1 and class size of 1.55-1.73 is 0.18, which are not equal.

525.

In a frequency distribution, the mid value of the class is 10 and width of the class is 6. Find the lower limit of the class.

Answer»

Consider the lower limit of the class as a

So the upper limit can be written as a + 6

We get

(a + (a + 6))/ 2 = 10

By cross multiplication

2a + 6 = 20

On further calculation

2a = 14

By division

a = 7

Class width = 6
Mid value = 10 cm

Half of Class width =
= 3

Lower limit of a class = Mid value - half of class width
= 10 - 3
= 7
----------------------------------------------------------------------------------------------------

If you were asked to find the upper limit of the class , then ,

Upper limit = Mid value + half of class width
= 10 + 3
= 13
526.

The class marks of a frequency distribution are 15, 20, 25, ………. .Find the class corresponding to the class mark 20.

Answer»

We know that

Class size = 20 – 15 = 5

Consider a as the lower limit of the required class

Upper limit can be written as a + 5

So we get

(a + (a + 5))/ 2 = 20

On further calculation

2a + 5 = 40

So we get

2a = 35

By division

a = 17.5

Upper limit a + 5 = 17.5 + 5 = 22.5

Therefore, the required class is 17.5-22.5

Given, CM= 15,20,25,30,35.....
Since the CM are of equal width, then class size= 20-15=5
Using the formula:
a+(h/2) and a-(h/2), Where a= CM and h=class size
Substituting,
20+(5/2)=20+2.5=22.5
20-(5/2)=20-2.5=17.5
Therefore, class (CM=20) is 22.5-17.5
Again,
25+(5/2)=25+2.5=27.5
and 25-(5/2)=25-2.5=22.5
Therefore, Class= 22.5-27.5
527.

The mid value of the class is used to calculateA) Mode B) Median C) Arithmetic Mean D) None of these

Answer»

Correct option is (C) Arithmetic Mean

The mid-value of the class is used to calculate arithmetic mean.

C) Arithmetic Mean

528.

If 1-5, 6-10, 11-15, ........, are classes of a frequency distribution, then the mid-value of class 11-15 is ______.

Answer» Correct Answer - 13
529.

The width of each of five continuous classes in a frequency distribution is 5 and lower class limit of the lowest class is 10. What is the upper class limit of the highest class?

Answer»

We know that lower limit of the lowest class = 10

It is given that

Width of each class = 5

Total number of classes = 5

So we get

First class = 10-15

Second class = 15-20

Third class = 20-25

Fourth class = 25-30

Fifth class = 30-35

Therefore, the upper class limit of the highest class is 35.

530.

Write mid-values of the following frequency distribution.Class Interval8-1112-1516-1920-2324-2728-3132-35Frequency4451320148

Answer»
C.IFrequencyMid - Values
8- 1149.5
12- 15413.5
16- 19517.5
20- 231321.5
24- 272025.5
28-311429.5
32- 35833.5

531.

The mid value of the class 10 – 19 is A) 14 B) 14.5C) 15 D) 15.5

Answer»

Correct option is (B) 14.5

Mid-value of the class 10–19 \(=\frac{10+19}2\)

= 14.5

Correct option is  B) 14.5

532.

The width of each of five continuous classes in a frequency distribution is 5 and the lower class-limit of the lowest class is 10. The upper class-limit of the highest class is:(A) 15(B) 25(C) 35(D) 40

Answer»

(C) 35

Explanation:

According to the question,

Since width of each five consecutive classes = 5

And, the lower limit of lowest class = 10

We get the data as follows,

10-15

15-20

20-25

25-30

30-35

Hence, we get upper limit of highest class = 35

Hence, option (C) is the correct answer.

533.

The mid value of 20-30 is `"_______"`.

Answer» Correct Answer - 25
534.

If 1-5 , 6 -10 , 11-15 , 16-20, ..., are the classes of a frequency distribution , then the lower boundary of the class 11-15 is `"_______"`.

Answer» Correct Answer - `10.5`
535.

0-10 , 10 - 20 , 20 - 30 , ...., are the classes , the lower boundary of the class 20-30 is `"_______"`.

Answer» Correct Answer - 20
536.

A data having two modes is A) unimodal data B) bi-modal data C) tri modal data D) none

Answer»

Correct option is (B) bi-modal data

A data having two modes is called bi-modal data.

B) bi-modal data

537.

For a data, the range is A) Maximum Value – Minimum Value B) Maximum Value + Minimum Value C) Maximum Value × Minimum Value D) Maximum Value / Minimum Value

Answer»

Correct option is (A) Maximum Value – Minimum Value

For a data, range = Maximum value - minimum value

A) Maximum Value – Minimum Value

538.

Two students collected two different data sets P and Q for a project. P :A table with the weights of all students of a class. The data was collected by a student for the project. Q: A table with lists of day wise absentees in a class. The data was collected by using the class attendance register. Which of the following is true about P and Q?A) P is primary data & Q is primary data B) P is secondary data & Q is primary data C) P is primary data & Q is secondary data D) P is secondary data & Q is secondary data

Answer»

C) P is primary data & Q is secondary data

539.

Let us now consider the following frequency distribution table which gives the weights of 38 students of a class:

Answer» we can add only in 35.5 to 40.5 class.
540.

Find the range of first five prime numbers.

Answer»

First five prime numbers 2, 3, 5, 7, 11. 

Maximum number = 11 

Minimum number = 2 

Range = 11 – 2 = 9

541.

In the given formula \(\overline x = \frac {\sum x_i}{n}\) what does n, \(\overline x \) denote.x = ∑ xi/n

Answer»

n = No. of observations

\(\overline x \) = Mean

542.

A teacher wanted to analysis the performance of two sections of students in a mathematics test of 100 marks. Looking performance, she found that a few students got under 20 marks and a few got 70 marks or above. So she decided to group them into intervals of varying sizes as follows : 0-20, 20-30, ....., 60-70, 70-100. Then she formed the following table : `|{:("Marks"," Number of students"),(0-20," 7"),(20-30," 10"),(30-40," 10"),(40-50," 20"),(50-60," 20"),(60-70," 15"),(70-"above"," 8"),("Total"," 90"):}|` (i) Find the probability that a student obtained less than `20%` in the mathematics test. (ii) Find the probability that a student obtained marks 60 or above .

Answer» Please refer to video to see the histogram for the given data table.
543.

The heights of boys and girls of IX class of a school are given below.Height135140147152155160Boys25121071Girls1210565Compare the heights of the boys and girls.

Answer»

HeightBoys (f)c.fGirls (f)c.f.
1352211
1405723
1471219\(\leftarrow\)1013
1521029518\(\leftarrow\)
155736624
160137529
N = 37N = 29

Boys median class = \(\frac {37+1}{2} = \frac {38}{2}\) = 19th

observation 

∴ Median height of boys = 147 cm

Girls median class = \(\frac {29+1}{2} = \frac {30}{2}\) = 15th

observation 

∴ Median height of girls = 152 cm

544.

All the students of a class performed poorly inMathematics. The teacher decided to give grace marks of 10 to each of thestudents. Which of the following statistical measures will not change evenafter the grace marks were given ?(1) median                               (2) mode(3) variance                             (4) mean

Answer» `y= x+10 ; bar(.y) = bar (.x) + 10 `
`sigma = sqrt((sum(x- bar (.x)))/n)`
`= sqrt((sum(y- 10 - bar(.y) + 10))/n)`
`= sqrt((sum(y- bar (.y)))/n)`
variance does not change
option 3 is correct
545.

Themean of the data set comprising of 16 observations is 16. If one of theobservation valued 16 is deleted and three new observations valued 3, 4 and 5are added to the data, then the mean of the resultant data, is :(1)16.8             (2) 16.0                  (3) 15.8               (4) 14.0

Answer» `(sum_(x=1)^16 x_i)/16 = 16`
`sum_(i=1)^16 x_i = 256`
`((sum x_i) - 16 + 3 + 4 + 5)/18 = (256 - 16 + 3 + 4 + 5)/18`
`= 252/18= 14`
option 3 is correct
546.

The mean (average) weight of three students is 40 kg. One of the students Ranga weighs 46 kg. The other two students, Rahim and Reshma have the same weight. Find Rahim’s weight.

Answer»

Weight of Ranga = 46 kg 

Weight of Reshma = Weight of Rahim = x kg say

Average = Sum of the weights/ Number = 40 kg

∴ 40 = \(\frac {46+x+x}{3}\)

3 x 40 = 46 + 2x 

2x = 120 – 46 = 74

∴ x = 74/2 = 37

∴ Rahim’s weight = 37 kg.

547.

If `barx_1,barx_2,barx_3,...barx_n` are the means of n groups with `n_1,n_2,n_3,....n_n` numbers of observations respectively. Than the mean `barx` of all group together is given by :A. `sum_(i=1)^(n)n_(i)bar(x)_(i)`B. `(sum_(i=1)^(n)n_(i)bar(x)_(i))/(n^(2))`C. `(sum_(i=1)^(n)n_(i)bar(x)_(i))/(sum_(i=1)^(n)n_(i))`D. `(sum_(i=1)^(n)n_(i)bar(x)_(i))/(2n)`

Answer» If `bar(x)_(1),bar(x)_(2), bar(x)_(3),……, bar(x)_(n)` are the means of n groups with `n_(1),n_(2),……, n_(n)` numbers of observations respectively, then the mean `bar(x)`
`bar(x) = (n_(1)bar(x)_(1)+n_(2)bar(x)_(2)+n_(3)bar(x)_(3)+.......+n_(n)bar(x)_(n))/(n_(1)+n_(2)+n_(3)+.....+n_(n))=(sum_(i=1)^(n)n_(i)bar(x)_(i))/(sum_(i=1)^(n)n_(i))`
Hence, the mean `bar(x)` of all group taken together is given by `(sum_(i=1)^(n)n_(i)bar(x)_(i))/(sum_(i=1)^(n)n_(i))`
So, (c) is the correct answer.
548.

Let `x_(1),x_(2),..,x_(n)` be n observations, and let x be their arithmetic mean and `sigma^(2)` be the variance Statement 1 : Variance of `2x_(1),2x_(2),..,2x_(n) " is" 4sigma^(2)`. Statement 2: Arithmetic mean `2x_(1),2x_(2),..,2x_(n)` is 4x.A. Statement 1 is false, statement 2 is true.B. Statement 1 is true, statement 2 is true, statement 2 is a correct explanation for statement 1.C. Statement 1 is true, statement 2 is true , statement 2 is not a correct explanation for statement 1.D. Statement 1 is true, statement 2 is false.

Answer» Correct Answer - D
A.M. of `2x_(1), 2x_(2)..2x_(n) " is" (2x_(1)+2x_(2)+..+2x_(n))/(n)`
`=2((x_(1)+x_(2)+..+x_(n))/(n))=2overline(x)`
So statement 2 is false.
variance `(2x_(i)=2^(2)` variance `(x_(i)=4sigma^(2)`
So statement 1 is true.
549.

The variance offirst 50 even natural numbers is(1) `(833)/4`(2) 833(3) 437(4) `(437)/4`

Answer» `2,4,6,8,......,98,100`
`sigma^2 = (sum x_1^2)/n - (bar(.x))^2`
`(2^2 + 4^2 + 6^2 + .... + 100^2)/50 - ((2+4+6 + ....+100)/50)^2`
`i_1 = (2^2+ 4^2 + 6^2 + ....+100^2)/50`
`= 2^2(1^2 + 2^2 + 3^2+ ...+50^2)/50`
`= 2^2/50 xx 50(50+1)(100+1)`
`=3434`
`i_2 = ((2+4+6+.....+100)/50)^2`
`= ((50 xx (2+100)/2)/50)^2`
`= (51)^2`
`sigma^2 = 3434 - 2661 = 833`
Answer
550.

The variance of first n natural number is:A. `(n^(2)-1)/(12)`B. `(n^(2)-1)/(6)`C. `(n^(2)+1)/(6)`D. `(n^(2)+1)/(12)`

Answer» Correct Answer - A
Variance`=(SD)^(2)=(1)/(n)sumx^(2)-((sum x)/(n))^(2), (because overline(x)=(sum x)/(n))`
`=(n(n+1)(2n+1))/(6n)-((n(n+1))/(2n))^(2)=(n^(2)-1)/(12)`