Math Problem Statement

Suppose the density function for a random variable X is given by f(x) .

It is known that the density function f(x) > 0 between -31.7 and 14 . Outside of that range, f(x) equals zero.

( Translation, the density curve is above the x-axis between the numbers -31.7 and 14. Otherwise, the density curve is the x-axis )

Determine F( 14 ) = P( X<= 14 )

Solution

We are asked to determine the value of F(14)=P(X14)F(14) = P(X \leq 14), where F(x)F(x) is the cumulative distribution function (CDF) of the random variable XX associated with the given probability density function (PDF) f(x)f(x).

The CDF is computed by integrating the PDF from the lower bound (in this case, -\infty) up to xx:

F(x)=P(Xx)=xf(t)dtF(x) = P(X \leq x) = \int_{-\infty}^{x} f(t) \, dt

In this case, we know the density function f(x)f(x) is non-zero only between 31.7-31.7 and 1414, and equals zero outside that range.

Thus, F(14)F(14), which represents P(X14)P(X \leq 14), will include the entire probability distribution between 31.7-31.7 and 1414. Since f(x)f(x) is a probability density function, the total area under the curve of f(x)f(x) over its support must equal 1:

F(14)=31.714f(x)dx=1F(14) = \int_{-31.7}^{14} f(x) \, dx = 1

Hence, F(14)=1F(14) = 1.

Conclusion:

F(14)=P(X14)=1F(14) = P(X \leq 14) = 1

Would you like further details, or do you have any questions?

Here are 5 related questions:

  1. How is the cumulative distribution function related to the probability density function?
  2. What are the properties of a probability density function?
  3. How would you compute F(x)F(x) for other values of xx?
  4. Can the cumulative distribution function F(x)F(x) ever decrease?
  5. What happens to F(x)F(x) as xx approaches infinity?

Tip: When integrating a PDF over its entire support, the result must always be 1, representing the total probability.

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Math Problem Analysis

Mathematical Concepts

Probability
Probability Density Function
Cumulative Distribution Function

Formulas

F(x) = P(X ≤ x) = ∫ f(t) dt from -∞ to x
F(14) = ∫ f(x) dx from -31.7 to 14

Theorems

Fundamental Theorem of Calculus
Properties of Probability Distributions

Suitable Grade Level

Grades 11-12 and College-level Probability