Continuous random variable question

In summary, the probability function for a continuous random variable x is f(X)=(X+1)/8 for -1<=X<=3 and 0 otherwise. To find the probability that X is less than or equal to 2, we can use the link between probability and the area under a density function. The mean of X can be calculated by finding the expected value of x, which is ∫ x * f(x) dx over the domain of definition of X. After solving for this, we get a mean of 5/3.
  • #1
dylbester
4
0
A continuous random variable x has the following probability function:
f(X)=(X+1)/8
-1<=X<=3
0 Otherwise

1. Find the Pr(X<=2)
2. Find the mean of X
 
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  • #2
Hello and welcome to MHB! :D

We ask that our users show their progress (work thus far or thoughts on how to begin) when posting questions. This way our helpers can see where you are stuck or may be going astray and will be able to post the best help possible without potentially making a suggestion which you have already tried, which would waste your time and that of the helper.

Can you post what you have done so far, here and in your other threads?
 
  • #3
mean of X is defined as ∫ x * f (x) dx over the domain of definition of X
∫ x (x + 1) / 8 dx
= ∫ (x^2 + x) / 8 dx
= x^3 / 24 + x^2 / 16 + c
Over the interval [-1, 3], we get:
(3^3 - (-1)^3) / 24 + (3^2 - (-1)^2) / 16
= 7/6 + 1/2
= 5/3

Im I right?
 
Last edited:
  • #4
Your calculation of the expected value (=mean) is correct. Have you already figured out how to compute $\mathbb{P}(X \leq 2)$?

Hint: use the link between a probability and the area under a density function
 

FAQ: Continuous random variable question

What is a continuous random variable?

A continuous random variable is a variable that can take on any numerical value within a given range. Unlike a discrete random variable, which can only take on specific, separate values, a continuous random variable can take on an infinite number of values within a range.

How is a continuous random variable different from a discrete random variable?

A continuous random variable is different from a discrete random variable in that it can take on an infinite number of values within a range, while a discrete random variable can only take on specific, separate values. Additionally, the probability distribution of a continuous random variable is described by a probability density function, while the probability distribution of a discrete random variable is described by a probability mass function.

What are some examples of continuous random variables?

Some examples of continuous random variables include height, weight, temperature, and time. These variables can take on an infinite number of values within a given range, and are not limited to specific, separate values.

How is a continuous random variable represented mathematically?

A continuous random variable is typically represented by the letter X, and its probability distribution is described by a probability density function (PDF). The PDF represents the relative likelihood of different values of the continuous random variable occurring, and the area under the curve of the PDF must equal 1.

How is the probability of a continuous random variable calculated?

The probability of a continuous random variable is calculated by finding the area under the curve of the probability density function (PDF) within a given range. This can be done using integrals in calculus. The probability of a continuous random variable taking on a specific value is always equal to 0, as the area under a single point on the PDF is infinitesimally small.

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