Which of the following random variables are discrete random variables?
(A) The number of defective bulbs in a box of 50 bulbs
(B) The time (in minutes) a customer waits at a bank counter
(C) The number of cars that come to a petrol pump in an hour
(D) The weight (in kg) of a newborn baby
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (C) only
A discrete random variable takes distinct, countable values (such as 0, 1, 2, …), with no value in between. A continuous random variable is obtained by measuring and can take every value in an interval.
So counts are discrete, and measured quantities such as time and weight are continuous.
Checking the statements
(A) The number of defective bulbs in a box of 50 bulbs — Correct. It is a count: 0, 1, 2, …, 50.
(B) The time a customer waits at a bank counter — Incorrect. Time is measured and can be any value such as 3.27 minutes, so it is continuous.
(C) The number of cars that come to a petrol pump in an hour — Correct. It is a count: 0, 1, 2, …
(D) The weight of a newborn baby — Incorrect. Weight is measured and can be any value in an interval, so it is continuous.