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ICT
October 12, 2023
Database-Management-System
October 12, 2023
ICT
October 12, 2023
Database-Management-System
October 12, 2023

Database-Management-System

Question 1
 A relation r(A, B) in a relational database has 1200 tuples. The attribute A has integer values ranging from 6 to 20, and the attribute B has integer values ranging from 1 to 20. Assume that the attributes A and B are independently distributed.

A
820
Question 1 Explanation: 

Explanation :

Probability of 1st condition being satisfied(say P(A)) = 10/15 = 2/3

Probability of 2nd condition being satisfied(say P(B)) = 1/20

Probability of both conditions being satisfied(say P(A intersection B)) = 2/3*1/20 = 1/30

Probability of any one condition being satisfied = P(A union B) = P(A)+P(B)-P(A intersection B) = 2/3 + 1/20 – 1/30 = 41/60

therefore, expected number of tuples = (41/60)*1200 = 820

Correct Answer: A
Question 1 Explanation: 

Explanation :

Probability of 1st condition being satisfied(say P(A)) = 10/15 = 2/3

Probability of 2nd condition being satisfied(say P(B)) = 1/20

Probability of both conditions being satisfied(say P(A intersection B)) = 2/3*1/20 = 1/30

Probability of any one condition being satisfied = P(A union B) = P(A)+P(B)-P(A intersection B) = 2/3 + 1/20 – 1/30 = 41/60

therefore, expected number of tuples = (41/60)*1200 = 820

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