Question

For a Normal Random Variable X with a mean of 80 and a Standard Deviation of 7, find P(X<80)

Is there a formula to figure this out?

Answer #1

Yes,

P[X<80]

=P[Z<0]

=0.5.........................by using normal probability table.

Given that x is a Normal random variable with a mean of 10 and
standard deviation of 4, find the following probabilities:
P(x<7.6)
P(x>11.5)
P(8.9<x<13.5)
Given that x is a Normal random variable with a mean of 10 and
standard deviation of 4, find x for each situation:
the area to the left of x is 0.1
the area to the left of x is 0.75
the area to the right of x is 0.35
the area to the right...

assume the random variable X is normally distributed with a mean 80
in standard deviation 9.4
find the P (x>72)
find the P (95<x<105)
find x so that the area above x is .80

A random variable is normally distributed with a mean of
80 and a standard deviation of 6.
a) Find P(X < 75.5)
b) Find P(X > 82)
c) Find P(77 < X < 84.8)

If X is a normal
random variable with a mean of 78 and a standard deviation of 5,
find the following probabilities:
a) P(X ≥ 78)
(1 Mark)
b) P(X ≥ 87)
(1 Mark)
c) P(X ≤ 91)
(1 Mark)
d) P(70
≤ X ≤ 77)
(1 Mark)

Suppose X is a normal random variable with mean
μ = 100 and standard deviation σ = 7. Find
b such that
P(100 ≤ X ≤
b) = 0.3.
HINT [See Example 3.] (Round your answer to one decimal
place.)
b =

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(2)Find the probabilities P(−4<X<0),P(−1<Y<0)
(3)Find the probabilities(let n size =8)
P(−4<X¯<0),P(3<Y¯<4)
(4)Find the 53th percentile of the distribution of X

Assume that the random variable X is normally distributed, with
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Given that x is a normal variable with mean ? = 114 and standard
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Find the value d such that P(20<X<d)=0.4641

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standard deviation equal to 5
a) P(x>55)=?
b) P(x<49)=?

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