# Math

X is a normal variable with mean 9. If P(X > 12) = 0.0062, calculate the standard deviation, the standard deviation if X.

1. 👍
2. 👎
3. 👁
1. (12-9)/sd = 2.5

I got 2.5 by finding the inv of .0062

3/sd = 2.5

3/2.5 = sd sd = 1.2

1. 👍
2. 👎

## Similar Questions

1. ### Statistics

Suppose that X , Y , and Z are independent, with E[X]=E[Y]=E[Z]=2 , and E[X2]=E[Y2]=E[Z2]=5 . Find cov(XY,XZ) . cov(XY,XZ)= Let X be a standard normal random variable. Another random variable is determined as follows. We flip a

2. ### probability

Let Θ be a Bernoulli random variable that indicates which one of two hypotheses is true, and let P(Θ=1)=p. Under the hypothesis Θ=0, the random variable X has a normal distribution with mean 0, and variance 1. Under the

3. ### probability

FUNCTIONS OF A STANDARD NORMAL The random variable X has a standard normal distribution. Find the PDF of the random variable Y, where: 1. Y=3X-1 , Y = 3X - 1 answer: fY(y)=1/3*fX*(y+1/3) f_ Y(y)=1/3*f_ X*(y+1/3) 2. Y=3X^2-1. For

4. ### Probability

CLT practice The random variables Xi are i.i.d. with mean 2 and standard deviation equal to 3. Assume that the Xi are nonnegative. Let Sn=X1+⋯+Xn. Use the CLT to find good approximations to the following quantities. You may want

1. ### Probability & Statistics

The random variable X has a standard normal distribution. Find the PDF of the random variable Y , where: 1. Y = 5X−7 . 2. Y = X2−2X . For y≥−1 ,

2. ### probability; math

Let X be a continuous random variable. We know that it takes values between 0 and 6 , but we do not know its distribution or its mean and variance, although we know that its variance is at most 4 . We are interested in estimating

3. ### Statistics

Normal distribution models what type of variable??

4. ### statistics

Given that z is a standard normal random variable, compute the following probabilities (to 4 decimals). P(z -1.0) P(z -1.0) P(z -1.5) P(z -2.5) P(-3 < z 0)

1. ### Science

Which of the following best describes the dependent variable in an experiment? A- the variable that is measured B- the variable that is manipulated C- the variable that you can see D- the variable that is most common (My guess is

2. ### stats

Let z be a random variable with a standard normal distribution, P(-1.9

3. ### algebra

in a relationship between variables, what is the variable called that changes in response to another variable? a. function b. input function c. independent variable d. dependent variable

4. ### physics

A space habitat for a long space voyage consists of two cabins each connected by a cable to a central hub as shown in the figure below. The cabins are set spinning around the hub axis, which is connected to the rest of the