# Ex 13.4, 14

Last updated at May 29, 2018 by Teachoo

Last updated at May 29, 2018 by Teachoo

Transcript

Ex 13.4, 14 A class has 15 students whose ages are 14, 17, 15, 14, 21, 17, 19, 20, 16, 18, 20, 17, 16, 19 and 20 years. One student is selected in such a manner that each has the same chance of being chosen and the age X of the selected student is recorded. What is the probability distribution of the random variable X? Find mean, variance and standard deviation of X. Let X be the age of student selected The age of student selected can be 14, 17, 15, 21, 19, 16, 18, 20 So, X can have the value 14, 15, 16, 17, 18, 19, 20, 21 The Probability distribution is given by : The Mean is given by : E = =1 =14 2 15 +15 1 15 +16 2 15 +17 3 15 +18 1 15 +19 2 15 +20 3 15 +21 1 15 = 28 + 15 + 32 + 51 + 18 + 38 + 60 + 21 15 = 263 15 = 17.53 Hence the mean is 17.53 The variance of x is given by : Var = 2 2 So, finding 2 E = = 1 2 = 14 2 2 15 + 15 2 1 15 + 16 2 2 15 + 17 2 3 15 + 18 2 1 15 + 19 2 2 15 + 20 2 3 15 + 21 2 1 15 = 196 2 + 225 1+256 2+289 3+324 1+361 2+400 3+441 1 15 = 392 + 225 + 512 + 867 + 324 + 722 + 1200 + 441 15 = Now, Var = = 4683 15 263 15 2 = 4683 15 69169 225 = 4683 15 69169 225 = 70245 69169 225 = 1076 225 = 4.78 Standard deviation is given by = ( ) = . = 2.18

Ex 13.4

Ex 13.4, 1

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Ex 13.4, 3 Important

Ex 13.4, 4 (i)

Ex 13.4, 4 (ii)

Ex 13.4, 4 (iii) Important

Ex 13.4, 5 (i) Important

Ex 13.4, 5 (ii)

Ex 13.4, 6 Important

Ex 13.4, 7 Important

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Ex 13.4, 9

Ex 13.4, 10 Deleted for CBSE Board 2022 Exams

Ex 13.4, 11 Important Deleted for CBSE Board 2022 Exams

Ex 13.4, 12 Important Deleted for CBSE Board 2022 Exams

Ex 13.4, 13 Important Deleted for CBSE Board 2022 Exams

Ex 13.4, 14 Deleted for CBSE Board 2022 Exams You are here

Ex 13.4, 15 Deleted for CBSE Board 2022 Exams

Ex 13.4, 16 (MCQ) Deleted for CBSE Board 2022 Exams

Ex 13.4, 17 (MCQ) Important Deleted for CBSE Board 2022 Exams

Chapter 13 Class 12 Probability (Term 2)

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About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.