Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Probability Distributions

Question:

If X is normal distribution random variable with mean $μ= 10$ and standard deviation $σ= 2$, Z is standard normal variable and F(Z) is cumulative distribution function, then which of the following are true?

[Given that $F(1.5) = 0.9332, F(3) = 0.9986, F(2.25) = 0.9878$ and $F(1) = 0.8413$]

(A) $P(X < 13) = 0.9332$
(B) $P(X >16) = 0.9986$
(C) $P(12 <X < 14.5) = 0.1465$
(D) $P(X > 8) = 0.8413$

Choose the correct answer from the options given below:

Options:

(A) and (D) only

(A), (B) and (C) only

(B), (C) and (D) only

(A), (C) and (D) only

Correct Answer:

(A), (C) and (D) only

Explanation:

The correct answer is Option (4) → (A), (C) and (D) only

Given $X$ is normal with $\mu=10,\;\sigma=2$

Standardization formula

$Z=\frac{X-\mu}{\sigma}=\frac{X-10}{2}$

(A) $P(X<13)$

$Z=\frac{13-10}{2}=1.5$

$P(X<13)=F(1.5)=0.9332$

(A) is true

(B) $P(X>16)$

$Z=\frac{16-10}{2}=3$

$P(X>16)=1-F(3)=1-0.9986=0.0014$

(B) is false

(C) $P(12<X<14.5)$

$Z_1=\frac{12-10}{2}=1$

$Z_2=\frac{14.5-10}{2}=2.25$

$P(12<X<14.5)=F(2.25)-F(1)=0.9878-0.8413=0.1465$

(C) is true

(D) $P(X>8)$

$Z=\frac{8-10}{2}=-1$

$P(X>8)=1-F(-1)=F(1)=0.8413$

(D) is true

The correct options are (A), (C) and (D).