Statistics and Probability

A game consists of spinning arrow which comes to rest pointing at one of the numbers

    \[\mathbf{1},\text{ }\mathbf{2},\text{ }\mathbf{3},\text{ }\mathbf{4},\text{ }\mathbf{5},\text{ }\mathbf{6},\text{ }\mathbf{7},\text{ }\mathbf{8},\text{ }\mathbf{9},\text{ }\mathbf{10},\text{ }\mathbf{11},\text{ }\mathbf{12};\]

as shown below. If the outcomes are equally likely, find the probability that the pointer will point at:

    \[\left( \mathbf{v} \right)\]

a number less than or equal to

    \[\mathbf{9}\]

    \[\left( \mathbf{vi} \right)\]

a number between

    \[\mathbf{3}\]

and

    \[\mathbf{11}\]

Solution: \[\left( v \right)\] Favorable outcomes for a number less than or equal to \[9\text{ }are\text{ }1,\text{ }2,\text{ }3,\text{ }4,\text{ }5,\text{ }6,\text{ }7,\text{ }8,\text{ }9\] So,...

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A game consists of spinning arrow which comes to rest pointing at one of the numbers

    \[\mathbf{1},\text{ }\mathbf{2},\text{ }\mathbf{3},\text{ }\mathbf{4},\text{ }\mathbf{5},\text{ }\mathbf{6},\text{ }\mathbf{7},\text{ }\mathbf{8},\text{ }\mathbf{9},\text{ }\mathbf{10},\text{ }\mathbf{11},\text{ }\mathbf{12};\]

as shown below. If the outcomes are equally likely, find the probability that the pointer will point at:

    \[~~~\left( \mathbf{iii} \right)\]

a prime number

    \[\left( \mathbf{iv} \right)\]

a number greater than

    \[\mathbf{8}\]

Solution: \[\left( iii \right)\]Favorable outcomes for a prime number are \[2,\text{ }3,\text{ }5,\text{ }7,\text{ }11\] So, number of favorable outcomes\[~=\text{ }5\] Hence, P(the pointer will be...

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A bag contains twenty Rs

    \[\mathbf{5}\]

coins, fifty Rs

    \[\mathbf{2}\]

coins and thirty Re

    \[\mathbf{1}\]

coins. If it is equally likely that one of the coins will fall down when the bag is turned upside down, what is the probability that the coin:

    \[\left( \mathbf{iii} \right)\]

will neither be a Rs

    \[\mathbf{5}\]

coin nor be a Re

    \[\mathbf{1}\]

coin?

Solution: \[\left( iii \right)\] Number of favourable outcomes for neither Re \[1\]nor Rs \[5\]coins \[=\] Number of favourable outcomes for Rs\[~2\] coins \[=\text{ }50\text{ }=\text{ }n\left( E...

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A bag contains twenty Rs

    \[\mathbf{5}\]

coins, fifty Rs

    \[\mathbf{2}\]

coins and thirty Re

    \[\mathbf{1}\]

coins. If it is equally likely that one of the coins will fall down when the bag is turned upside down, what is the probability that the coin:

    \[\left( \mathbf{i} \right)\]

will be a Re

    \[\mathbf{1}\]

coin?

    \[\left( \mathbf{ii} \right)\]

will not be a Rs

    \[\mathbf{2}\]

coin?

Solution: We have, Total number of coins \[=\text{ }20\text{ }+\text{ }50\text{ }+\text{ }30\text{ }=\text{ }100\] So, the total possible outcomes \[=\text{ }100\text{ }=\text{ }n\left( S \right)\]...

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In a bundle of

    \[\mathbf{50}\]

shirts,

    \[\mathbf{44}\]

are good,

    \[\mathbf{4}\]

have minor defects and

    \[\mathbf{2}\]

have major defects. What is the probability that:

    \[\left( \mathbf{i} \right)\]

it is acceptable to a trader who accepts only a good shirt?

    \[\left( \mathbf{ii} \right)\]

it is acceptable to a trader who rejects only a shirt with major defects?

Solution: We have, Total number of shirts \[=\text{ }50\] Total number of elementary events \[=\text{ }50\text{ }=\text{ }n\left( S \right)\] \[\left( i \right)\] As, trader accepts only good shirts...

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A bag contains

    \[\mathbf{3}\]

red balls,

    \[\mathbf{4}\]

blue balls and

    \[\mathbf{1}\]

yellow ball, all the balls being identical in shape and size. If a ball is taken out of the bag without looking into it; find the probability that the ball is:

    \[\left( \mathbf{iii} \right)\]

not yellow

    \[\left( \mathbf{iv} \right)\]

neither yellow nor red

Solution: \[\left( iii \right)\] Probability of not drawing a yellow ball \[=\text{ }1\text{ }\] Probability of drawing a yellow ball Thus, probability of not drawing a yellow ball \[=\text{...

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A bag contains

    \[\mathbf{3}\]

red balls,

    \[\mathbf{4}\]

blue balls and

    \[\mathbf{1}\]

yellow ball, all the balls being identical in shape and size. If a ball is taken out of the bag without looking into it; find the probability that the ball is:

    \[\left( \mathbf{i} \right)\]

yellow

    \[\left( \mathbf{ii} \right)\]

red

Solution: The total number of balls in the bag \[=\text{ }3\text{ }+\text{ }4\text{ }+\text{ }1\text{ }=\text{ }8\] balls So, the number of possible outcomes \[=\text{ }8\text{ }=\text{ }n\left( S...

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multiple Nine cards (identical in all respects) are numbered . A card is selected from them at random. Find the probability that the card selected will be:

    \[\left( \mathbf{iii} \right)\]

an even number and a multiple of

    \[\mathbf{3}\]

    \[\left( \mathbf{iv} \right)\]

an even number or a of

    \[\mathbf{3}\]

Solution: \[\left( iii \right)\] From numbers \[2\text{ }to\text{ }10\], there is one number which is an even number as well as multiple of \[3\text{ }i.e.\text{ }6\] So, favorable number of events...

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The monthly income of 100 families are given as below : Income (in Rs) Number of families 0-5000 8 5000-10000 26 10000-15000 41 15000-20000 16 20000-25000 3 25000-30000 3 30000-35000 2 35000-40000 1 Calculate the modal income.

  As per the information given, The most elevated recurrence = 41, 41 lies in the stretch 10000 – 15000. Here, l = 10000, fm = 41,f1 = 26,f2 = 16 and h = 5000 \[=\text{ }10000\text{ }+\text{...

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The maximum bowling speeds, in km per hour, of 33 players at a cricket coaching centre are given as follows: Speed (km/h) 85-100 100-115 115-130 130-145 Number of players 11 9 8 5 Calculate the median bowling speed.

First we develop the combined recurrence table Speed ( in km/h)               Number of players           Cumulative recurrence 85 – 100              11           11 100 – 115           ...

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Weekly income of 600 families is tabulated below : Weekly income Number of families (in Rs) 0-1000 250 1000-2000 190 2000-3000 100 3000-4000 40 4000-5000 15 5000-6000 5 Total 600 Compute the median income.

Week by week Income   Number of families (fi)   Cumulative recurrence (cf) 0-1000  250        250 1000-2000           190        250 + 190 = 400 2000-3000           100        440 + 100 = 540...

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Given below is a cumulative frequency distribution showing the marks secured by 50 students of a class: Marks Below 20 Below 40 Below 60 Below 80 Below 100 Number of students 17 22 29 37 50 Form the frequency distribution table for the data.

The recurrence circulation table for given information. Marks    Number of understudies 0 – 20    12 20 – 40  22 – 17 = 5 40 – 60  29 – 22 = 7 60 – 80  37 – 29 = 8 80 – 100              50 – 37 =...

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The following are the ages of 300 patients getting medical treatment in a hospital on a particular day: Age (in years) 10-20 20-30 30-40 40-50 50-60 60-70 Number of patients 60 42 55 70 53 20 Form: ALess than type cumulative frequency distribution. More than type cumulative frequency distribution

  (I) Less than type Age (in year)       Number of patients Under 10             0 Under 20             60 + 0 = 60 Under 30             60 + 42 = 102 Under 40             102 + 55 = 157 Under...

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Find the unknown entries a, b, c, d, e, f in the following distribution of heights of students in a class: Height Frequency Cumulative frequency (in cm) 150-155 12 a 155-160 b 25 160-165 10 c 165-170 d 43 170-175 e 48 175-180 2 f Total 50

  Tallness (in cm)  Frequency           Cumulative recurrence given       Cumulative recurrence 150 – 155            12           a             12 155 – 160            b            ...

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Form the frequency distribution table from the following data : Marks (out of 90) Number of candidates More than or equal to 80 4 More than or equal to 70 6 More than or equal to 60 11 More than or equal to 50 17 More than or equal to 40 23 More than or equal to 30 27 More than or equal to 20 30 More than or equal to 10 32 More than or equal to 0 34

The recurrence dissemination table for the given information is: Class Interval      Number of understudies 0-10       34 – 32 = 2 10-20     32 – 30 = 2 20-30     30 – 27 = 3 30-40     27 – 23 = 4...

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The following table shows the cumulative frequency distribution of marks of 800 students in an examination: Marks Number of students Below 10 10 Below 20 50 Below 30 130 Below 40 270 Below 50 440 Below 60 570 Below 70 670 Below 80 740 Below 90 780 Below 100 800 Construct a frequency distribution table for the data above.

The recurrence circulation table for the given information is: Class Interval      Number of understudies 0-10       10 10-20     50 – 10 = 40 20-30     130 – 50 = 80 30-40     270 – 130 = 140...

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The following is the distribution of weights (in kg) of 40 persons : Weight (in kg) 40-45 45-50 50-55 55-60 60-65 65-70 70-75 75-80 Number of persons 4 4 13 5 6 5 2 1 Construct a cumulative frequency distribution (of the less than type) table for the data above.

Weight (in kg)    Cumulative recurrence Under 45             4 Under 50             4 + 4 = 8 Under 55             8 + 13 = 21 Under 60             21 + 5 = 26 Under 65             26 + 6 = 32 Under...

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The mileage (km per litre) of 50 cars of the same model was tested by a manufacturer and details are tabulated as given below : Mileage (km/l) 10-12 12-14 14-16 16-18 Number of cars 7 12 18 13 Find the mean mileage. The manufacturer claimed that the mileage of the model was 16 km/litre. Do you agree with this claim?

Mileage (km L-1)              Class – Marks (xi)             Number of vehicles (fi)   fixi 10 – 12  11           7             77 12 – 14  13           12           156 14 – 16  15          ...

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The weights (in kg) of 50 wrestlers are recorded in the following table : Weight (in kg) 100-110 110-120 120-130 130-140 140-150 Number of wrestlers 4 14 21 8 3 Find the mean weight of the wrestlers.

Weight (in kg)    Number of Wrestlers (fi)               Class Marks (xi)  Deviation (di = xi – a) fidi 100 – 110            4             105        –20        –80 110 – 120            14          ...

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An aircraft has 120 passenger seats. The number of seats occupied during 100 flights is given in the following table : Number of seats 100-104 104-108 108-112 112-116 116-120 Frequency 15 20 32 18 15 Determine the mean number of seats occupied over the flights.

  Class Interval      Class Marks (xi)  Frequency (fi)     Deviation (di = xi – a)      fidi 100 – 104            102        15           –8           –120 104 – 108            106       ...

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The daily income of a sample of 50 employees are tabulated as follows : Income (in Rs) 1-200 201-400 401-600 601-800 Number of employees 14 15 14 7 Find the mean daily income of employees.

C.I          xi            di = (xi – a)          Fi            fidi 1 – 200  100.5     –200      14           –2800 201 – 400            300.5     0             15           0 401 – 600           ...

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The following tabe gives the number of pages written by Sarika for completing her own book for 30 days : Number of pages written per day 16-18 19-21 22-24 25-27 28-30 Number of days 1 3 4 9 13 Find the mean number of pages written per day.

Class Marks         Mid – Value (xi) Number of days (fi)         fixi 15.5 – 18.5          17           1             17 18.5 – 21.5          20           3             60 21.5 – 24.5         ...

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In calculating the mean of grouped data, grouped in classes of equal width, we may use the formula where a is the assumed mean. a must be one of the mid-points of the classes. Is the last statement correct? Justify your answer.

No, the assertion isn't right. It isn't required that expected mean ought to be the mid – mark of the class span. a can be considered as any worth which is not difficult to work on it.

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Apoorv throws two dice once and computes the product of the numbers appearing on the dice. Peehu throws one die and squares the number that appears on it. Who has the better chance of getting the number 36? Why?

Apoorv toss two dice on the double. Thus, the all out number of results = 36 Number of results for getting item 36 = 1(6×6) ∴ Probability for Apoorv = 1/36 Peehu tosses one kick the bucket, Thus,...

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Consider the following distribution : Marks obtained Number of students More than or equal to 0 63 More than or equal to 10 58 More than or equal to 20 55 More than or equal to 30 51 More than or equal to 40 48 More than or equal to 50 42 The frequency of the class 30-40 is (A) 3 (B) 4 (C) 48 (D) 51

(A) 3 Clarification: Imprints Obtained            Number of students        Cumulative Frequency 0-10       (63 – 58) = 5       5   10-20     (58 – 55) = 3       3   20-30     (55 – 51) =...

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The times, in seconds, taken by 150 athletes to run a 110 m hurdle race are tabulated below Class 13.8-14 14-14.2 14.2-14.4 14.4-14.6 14.6-14.8 14.8-15 Frequency 2 4 5 71 48 20 The number of athletes who completed the race in less than 14.6 seconds is : A11 (B) 71 (C) 82 (D) 130

(C) 82 Clarification: The quantity of competitors who finished the race in under 14.6 second= 2 + 4 + 5 + 71 = 82 Subsequently, choice (C) is right

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Consider the data : Class 65-85 85-105 105-125 125-145 145-165 165-185 185-205 Frequency 4 5 13 20 14 7 4 The difference of the upper limit of the median class and the lower limit of the modal class is A0 (B) 19 (C) 20 (D) 38

(C) 20 Clarification: Class      Frequency           Cumulative Frequency   65-85     4             4   85-105  5             9   105-125               13           22  ...

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For the following distribution: Marks Number of students Below 10 3 Below 20 12 Below 30 27 Belo w 40 57 Below 50 75 Below 60 80 The modal class is (A)10-20 (B) 20-30 (C) 30-40 (D) 50-60

(C) 30-40 Clarification: Marks    Number of students        Cumulative Frequency   Underneath 10  3=3        3   10-20     (12 – 3) = 9         12   20-30     (27 – 12) = 15     27...

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For the following distribution : Class 0-05 5-10 10-15 15-20 20-25 Frequency 10 15 12 20 9 the sum of lower limits of the median class and modal class is (A)15 (B) 25 (C) 30 (D) 35

(B) 25 Clarification: Class      Frequency           Cumulative Frequency   0-5         10           10   5-10       15           25   10-15     12           37   15-20    ...

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While computing mean of grouped data, we assume that the frequencies are (A) Evenly distributed over all the classes (B) Centred at the class marks of the classes (C) Centred at the upper limits of the classes (D) Centred at the lower limits of the classes

(B) Centered at the class characteristics of the classes Clarification: In figuring the mean of assembled information, the frequencies are focused at the class signs of the classes. Subsequently,...

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Choose the correct answer from the given four options: 1. In the formula For finding the mean of grouped data di’s are deviations from a of (A) Lower limits of the classes (B) Upper limits of the classes (C) Mid points of the classes (D) Frequencies of the class marks

(C) Mid marks of the classes Clarification: We know, \[di\text{ }=\text{ }xi\text{ }\text{ }a\] Where, xi are information and 'a' is the expected to be mean In this way, di are the deviations from...

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