Math Problem Statement

An expensive piece of equipment in a laboratory is starting to show signs of age. Let X be the number of days in any week that the equipment is working and suppose that X has the following probability distribution:

x 0 1 2 3 4 5 P(X=x) 0.01 0.09 0.25 0.34 0.24 0.07 In Quiz 3 we calculated the expected value and standard deviation of X.

The probabilities for X actually come from a Binomial distribution with n = 5 trials. The parameter p for this Binomial distribution is

Solution

To find the parameter pp of the Binomial distribution that matches the given probabilities, we'll use the properties of the Binomial distribution.

The Binomial distribution is defined as:

P(X=x)=(nx)px(1p)nxP(X = x) = \binom{n}{x} p^x (1-p)^{n-x}

Given:

  • n=5n = 5
  • The probabilities P(X=x)P(X = x) for x=0,1,2,3,4,5x = 0, 1, 2, 3, 4, 5 are provided.

To find pp, we should use the fact that for a Binomial distribution:

E(X)=np\text{E}(X) = np

We can calculate the expected value E(X)\text{E}(X) using the provided distribution and then set it equal to 5p5p (since n=5n = 5).

Step 1: Calculate the Expected Value E(X)\text{E}(X)

E(X)=x=05xP(X=x)\text{E}(X) = \sum_{x=0}^{5} x \cdot P(X = x)

Substituting the given probabilities:

E(X)=00.01+10.09+20.25+30.34+40.24+50.07\text{E}(X) = 0 \cdot 0.01 + 1 \cdot 0.09 + 2 \cdot 0.25 + 3 \cdot 0.34 + 4 \cdot 0.24 + 5 \cdot 0.07

E(X)=0+0.09+0.5+1.02+0.96+0.35=2.92\text{E}(X) = 0 + 0.09 + 0.5 + 1.02 + 0.96 + 0.35 = 2.92

Step 2: Find pp

Given E(X)=np\text{E}(X) = np:

2.92=5p2.92 = 5p

p=2.925=0.584p = \frac{2.92}{5} = 0.584

Thus, the parameter pp for this Binomial distribution is approximately 0.584.

Would you like more details on this process or have any questions?

Here are 5 related questions for further exploration:

  1. How would the distribution change if the parameter pp was slightly higher?
  2. What is the variance of XX for this Binomial distribution?
  3. How does the Binomial distribution relate to the Normal distribution for large nn?
  4. How would you calculate the probability of the equipment working for exactly 4 days?
  5. What does the standard deviation tell you about the reliability of the equipment?

Tip: When dealing with distributions, understanding both the mean and the variance is crucial for interpreting the behavior of random variables.

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Math Problem Analysis

Mathematical Concepts

Probability Theory
Binomial Distribution
Expected Value
Probability Mass Function

Formulas

Binomial distribution formula: \( P(X = x) = \binom{n}{x} p^x (1-p)^{n-x} \)

Theorems

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Suitable Grade Level

Advanced High School