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Find the variance and standard deviation of the numbers: 4, 6, 8, 10, 12.

Mathematics

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Answer

8\text{8}

222\sqrt{2}

Step-by-step solution

4 steps
  1. Calculate the mean (xˉ\bar{x}) of the numbers.

    The given numbers are 4,6,8,10,124, 6, 8, 10, 12. There are n=5n=5 numbers.

    xˉ=∑xn=4+6+8+10+125=405=8\bar{x} = \frac{\sum x}{n} = \frac{4 + 6 + 8 + 10 + 12}{5} = \frac{40}{5} = 8
  2. Calculate the sum of the squared differences from the mean, ∑(x−xˉ)2\sum (x - \bar{x})^2.

    (4−8)2=(−4)2=16(6−8)2=(−2)2=4(8−8)2=(0)2=0(10−8)2=(2)2=4(12−8)2=(4)2=16\begin{align*} (4 - 8)^2 &= (-4)^2 = 16 \\ (6 - 8)^2 &= (-2)^2 = 4 \\ (8 - 8)^2 &= (0)^2 = 0 \\ (10 - 8)^2 &= (2)^2 = 4 \\ (12 - 8)^2 &= (4)^2 = 16 \end{align*} ∑(x−xˉ)2=16+4+0+4+16=40\sum (x - \bar{x})^2 = 16 + 4 + 0 + 4 + 16 = 40
  3. Calculate the variance (σ2\sigma^2).

    σ2=∑(x−xˉ)2n=405=8\sigma^2 = \frac{\sum (x - \bar{x})^2}{n} = \frac{40}{5} = 8

    The variance is 8\boxed{\text{8}}.

  4. Calculate the standard deviation (σ\sigma).

    The standard deviation is the square root of the variance.

    σ=σ2=8=4×2=22≈2.83\sigma = \sqrt{\sigma^2} = \sqrt{8} = \sqrt{4 \times 2} = 2\sqrt{2} \approx 2.83

    The standard deviation is 22\boxed{2\sqrt{2}}.

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