Standard Deviation Math Example 2

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Example 2

hard
Find the sample standard deviation of {10,12,23,23,16,23,21,16}\{10, 12, 23, 23, 16, 23, 21, 16\}.

Solution

  1. 1
    Compute the sample mean: xห‰=10+12+23+23+16+23+21+168=1448=18\bar{x} = \frac{10+12+23+23+16+23+21+16}{8} = \frac{144}{8} = 18.
  2. 2
    Squared deviations: (10โˆ’18)2=64(10-18)^2=64, (12โˆ’18)2=36(12-18)^2=36, (23โˆ’18)2=25(23-18)^2=25 (three times), (16โˆ’18)2=4(16-18)^2=4 (twice), (21โˆ’18)2=9(21-18)^2=9.
  3. 3
    Sum: 64+36+25+25+4+25+9+4=19264 + 36 + 25 + 25 + 4 + 25 + 9 + 4 = 192.
  4. 4
    Sample variance (divide by nโˆ’1=7n-1 = 7): s2=1927โ‰ˆ27.43s^2 = \frac{192}{7} \approx 27.43.
  5. 5
    Sample standard deviation: s=27.43โ‰ˆ5.24s = \sqrt{27.43} \approx 5.24.

Answer

sโ‰ˆ5.24s \approx 5.24
The sample standard deviation uses nโˆ’1n - 1 in the denominator (Bessel's correction) to provide an unbiased estimate of the population standard deviation when working with a sample.

About Standard Deviation

The standard deviation measures the average distance of data values from the mean, giving a typical spread around the center.

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