Chapter 9.3, Problem 21E

### Calculus: An Applied Approach (Min...

10th Edition
Ron Larson
ISBN: 9781305860919

Chapter
Section

### Calculus: An Applied Approach (Min...

10th Edition
Ron Larson
ISBN: 9781305860919
Textbook Problem
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# Using Technology In Exercises 17-22, use a symbolic integration utility to find the mean, variance, and standard deviation of the probability density function. Then find the percent of the distribution that lies within the given standard deviations of the mean. See Example 3. Function StandardDeviations f ( x ) = 1 2 2 π e − ( x − 8 ) 2 / 8 , − ∞ < x < ∞        2

To determine

To calculate: The mean, variance and standard deviation of probability density function

f(x)=11.52πe(x8)28

The percentage of the distribution that lies within the given standard deviation 1 of the mean.

Explanation

Given Information:

The provided equation is,

f(x)=11.52πe(x8)28

And the standard deviation is 1.

Formula used:

If f is a probability density function of a continuous random variable x over the interval [a,b] then the mean of x is given by,

μ=E(x)=abxf(x)dx

The variance is given by,

V(x)=ab(xμ)2f(x)dxorV(x)=abx2f(x)dxμ2

The standard deviation of x is,

σ=V(x)

To find the percent of distribution that lies within one standard deviation of the mean integrate f(x) between μ and μ+σ,

Percentage =μσμ+σf(x)dx

Calculation:

Consider the function,

f(x)=11.52πe(x8)28

For the mean of the function,

f(x)=11.52πe(x8)28μ=11.52πxe(x8)28dx=11.52π0xe(x8)28dx=2[e(x8)28]0

Further simplify,

μ=6860=8

For the Variance of the function,

f(x)=11

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