Math Problem Statement

A random variable X is uniformly distributed between 4 and 12. The height of the uniform distribution is 1/8.

Find the probability that X is at most 7 as shown in the sketch below. 345678910111213[Graphs generated by this script: setBorder(0,30,0,0);initPicture(2.5,13.5,0,1);axes(1,100,1,0,0,1,0);path([[2.5,0],[4,0],[4,.8],[12,.8],[12,0],[13.5,0]]);fill='blue';rect([4,0],[7,.8]);]

Give the probability as a fraction or as a decimal rounded to four decimal places.

P(X is at most 7)=      

Solution

Given that the random variable XX is uniformly distributed between 4 and 12, with a height of 18\frac{1}{8}, the probability that XX is at most 7 can be found by calculating the area under the probability density function (PDF) from 4 to 7.

Step 1: Length of the interval

The uniform distribution is defined between 4 and 12. The total length of the interval is: 124=812 - 4 = 8

Step 2: PDF of uniform distribution

The height of the uniform distribution is given as 18\frac{1}{8}. This means that the probability density is uniform (constant) over the interval [4, 12].

Step 3: Calculating the area for X7X \leq 7

The probability that XX is at most 7 is the area of the rectangle under the PDF from 4 to 7. The length of this subinterval is: 74=37 - 4 = 3 The area under the PDF is the length of this interval multiplied by the height of the uniform distribution, which is 18\frac{1}{8}: Area=(74)×18=3×18=38=0.375\text{Area} = (7 - 4) \times \frac{1}{8} = 3 \times \frac{1}{8} = \frac{3}{8} = 0.375

Final Answer:

P(X7)=0.375P(X \leq 7) = 0.375 Thus, the probability that XX is at most 7 is 0.3750.375 (or 38\frac{3}{8}).

Would you like further details or have any questions?

Here are five related questions:

  1. What is the probability that XX is between 5 and 10?
  2. How would the probability change if XX was uniformly distributed between 3 and 15?
  3. What is the cumulative distribution function (CDF) for XX in this uniform distribution?
  4. Can you calculate the mean and variance of a uniform distribution?
  5. How does a uniform distribution compare to a normal distribution?

Tip: For uniform distributions, the probability is always proportional to the length of the interval of interest.

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Math Problem Analysis

Mathematical Concepts

Probability
Uniform Distribution

Formulas

Area under the PDF = (b - a) * height

Theorems

Uniform Distribution Probability Theorem

Suitable Grade Level

Grades 10-12