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Find the standard deviation for the given probability distribution.xp(X)x.P(X)x2.P(X)00.21  10.08  20.08  30.36  40.27

Question

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Solution

1. Break Down the Problem

To find the standard deviation of a probability distribution, we will go through the following steps:

  1. Calculate the expected value (mean).
  2. Calculate the variance.
  3. Find the square root of the variance to get the standard deviation.

2. Relevant Concepts

  • Mean (μ): μ=(xP(X)) \mu = \sum (x \cdot P(X))
  • Variance (σ²): σ2=(x2P(X))μ2 \sigma^2 = \sum (x^2 \cdot P(X)) - \mu^2
  • Standard Deviation (σ): σ=σ2 \sigma = \sqrt{\sigma^2}

3. Analysis and Detail

Let’s gather the values from the probability distribution:

x P(X) x * P(X) x² * P(X)
0 0.21 0 0
1 0.08 0.08 0.08
2 0.08 0.16 0.32
3 0.36 1.08 3.24
4 0.27 1.08 4.32

Step 1: Calculate the Expected Value (μ)

μ=(xP(X))=0+0.08+0.16+1.08+1.08=2.4 \mu = \sum (x \cdot P(X)) = 0 + 0.08 + 0.16 + 1.08 + 1.08 = 2.4

Step 2: Calculate the Variance (σ²)

σ2=(x2P(X))μ2 \sigma^2 = \sum (x^2 \cdot P(X)) - \mu^2 Calculating (x2P(X)) \sum (x^2 \cdot P(X)) : (x2P(X))=0+0.08+0.32+3.24+4.32=8.96 \sum (x^2 \cdot P(X)) = 0 + 0.08 + 0.32 + 3.24 + 4.32 = 8.96 Now, substituting to find variance: σ2=8.96(2.4)2=8.965.76=3.2 \sigma^2 = 8.96 - (2.4)^2 = 8.96 - 5.76 = 3.2

4. Verify and Summarize

Calculating the standard deviation: σ=σ2=3.21.79 \sigma = \sqrt{\sigma^2} = \sqrt{3.2} \approx 1.79

Final Answer

The standard deviation for the given probability distribution is approximately σ1.79 \sigma \approx 1.79 .

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