JEE MainMathematicsStatisticsMCQ+4 / −1
Three rotten apples are mixed accidently with seven good apples and four apples are drawn one by one without replacement. Let the random variable X denote the number of rotten apples. If and represent mean and variance of X, respectively, then is equal to :
- A20
- B30
- C250
- D25
View written solutionFree
Correct answer: A
- Identify the distribution
There are:
- rotten apples
- good apples
- total apples
We draw apples without replacement.
If = number of rotten apples drawn, then follows a hypergeometric distribution with parameters: where:
- = total population size
- = number of rotten apples
- = number of draws
- Find the mean
For a hypergeometric random variable, So,
Thus,
- Find the variance
For a hypergeometric random variable, Substitute the values: Now simplify: So,
Thus,
- Compute
Therefore,
- Compute the required value
- Check options
The correct option is: So, Option A is correct.
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