# Probability (ISS (Statistical Services) Statistics Paper I (Old Subjective Pattern)): Questions 33 - 38 of 72

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## Question number: 33

» Probability » Distribution Function » Standard Probability Distributions

Appeared in Year: 2015

### Describe in Detail

Let Y _{1} denote the first order statistic in a random sample of size n from a distribution that has the pdf

Obtain the distribution of Z _{n} =n (Y _{1} -θ).

### Explanation

To find the distribution of order statistic, the pdf is

Here denote the first order statistic that is

The cdf of x is

The pdf of Y _{1} is

Then, the distribution of Z _{n} =n (Y _{1} -θ) is

## Question number: 34

» Probability » Distribution Function » Standard Probability Distributions

Appeared in Year: 2013

### Describe in Detail

Find the distribution of the ratio of two iid random variables with density function:

### Explanation

Let consider x and y are two iid random variable with density function is same. Then find the distribution of their ratio that is x/y. The joint pdf of x and y is

To find this we use Jacobian transformation technique, assume

X/Y = u, Y = v

X

## Question number: 35

» Probability » Standard Probability Distributions » Normal

Appeared in Year: 2012

### Describe in Detail

12.3 % of the candidates in a public examination score at least 70%, while another 6.3 % score at most 30%. Assuming the underlying distribution to be normal, estimate the percentage of candidates scoring 80 % or more.

### Explanation

Let total marks obtain is 100. Assuming the underlying distribution to be normal, the mean µ and variance σ ^{2}. It is given that

The value of z corresponding to an area

0.500 - 0.123 = 0.377

We can write

Similarly, . It is given that

## Question number: 36

» Probability » Probability of M Events Out of N

Appeared in Year: 2013

### Describe in Detail

A fair die is rolled twice. Let A be the event that the first throw shows a number ≤ 2, and B be the event that the second throw shows at least 5. Show that P (AUB) =5/9.

### Explanation

A fair die is rolled twice, the sample space consists of thirty six outcomes. The sample space is

(1, 1), (1, 2), (1, 3), (1, 4), (1, 5), (1, 6)

(2, 1), (2, 2), (2, 3), (2, 4), (2, 5), (2, 6)

(3, 1), (3, 2), (3, 3), (3, 4),

## Question number: 37

» Probability » Probability of M Events Out of N

Appeared in Year: 2014

### Describe in Detail

A positive integer X is selected at random from the first 50 natural numbers.

Calculate P (X + 96/X > 50).

### Explanation

Total number of possible outcomes = number of ways in which the one random number can be chosen out of 50

Let Y be the event whose satisfied the relation, X + 96/X > 50

For which X we choose is

So, X takes values

## Question number: 38

» Probability » Elements of Measure Theory

Appeared in Year: 2014

### Describe in Detail

Suppose that all the four outcomes 0 _{1}, 0 _{2}, 0 _{3} and 0 _{4} of an experiment are equally likely. Define A = (0 _{1}, 0 _{4}), B = (0 _{2}, 0 _{4}) and C = (0 _{3}, 0 _{4}). What can you say about the pairwise independence and mutually independence of the events A, B and C?

### Explanation

Given that there are four outcomes. Define A = (O _{1}, O _{4}), B = (O _{2}, O _{4}), C = (O _{3}, O _{4})

Their intersection is and Union is AUBUC = (O _{1}, O _{2}, O _{3}, O