Question

X and Y are both standard normal random variables (mean = 0, standard deviation = 1), statistically independent of each other. Using the DATA IN THE ATTACHED FILE, estimate the probability that X and Y are both positive and that their sum is less or equal to 1. This probability is

Answer 1

Answer:

The probability that X and Y are both positive and that their sum is less or equal to 1 0.64.

Step-by-step explanation:

It is provided that the random variables X and Y follows a standard normal distribution.

That is, $X,Y\sim N(0, 1)$

It is also provided that the variables X and Y are statistically independent of each other.

Compute the probability that X and Y are both positive and that their sum is less or equal to 1 as follows:

The mean and standard deviation of X + Y are:

$E(X+Y)=E(X)+E(Y)=0+0=0\\\\SD(X+Y)=\sqrt{V(X)+V(Y)+2Cov(X,Y)}=\sqrt{1+1+0}=\sqrt{2}$

The probability is:

$P(X+Y\leq 1)=P(X+Y$

                       $=P(X+Y$

*Use the z-table.

Thus, the probability that X and Y are both positive and that their sum is less or equal to 1 0.64.