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In applied life data analysis (wiley, 1982), wayne nelson presents the breakdown time of an insulating fluid between electrodes at 34 kv. the times, in minutes, are as follows: 0.05, 0.93, 0.92, 1.18, 2.87, 3.30, 4.30, 4.68, 4.78, 6.46, 7.29, 7.88, 8.36, 12.16, 31.66, 32.59, 33.88, 36.80, and 72.89. calculate the sample mean and sample standard deviation. round the answers to 3 decimal places.

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Matheng
The mean = 14.36736842

The sample standard deviation = 18.882

See the attached figure for the detailed solution.
Ver imagen Matheng
The correct answers are:
Sample mean = 14.367
Sample standard deviation = 18.882

Explanation:
To find the sample mean, we first find the sum of the data values.  This is 272.98.  We next divide this by the number of data points, 19:
272.98/19 = 14.367

The first step in finding the sample standard deviation is to subtract the mean from each data point.  This gives us the following values:
-14.31, -13.43, -13.44, -13.18, -11.49, -11.06, -10.06, -9.687, -9.587, -7.907, -7.077, -6.487, -6.007, -2.207, 17.293, 18.223, 19.513, 22.433, 58.523.

Next we square these values.  This gives us the following list of values:
204.97, 180.55, 180.82, 173.89, 132.18, 122.47, 101.34, 93.837, 91.91, 62.52, 50.083, 42.081, 36.084, 4.8708, 299.04, 332.07, 380.75, 503.23, 3424.9

Next we find the sum of these values.  This is 6417.705.

The next step is to divide this sum by n-1, where n is the number of data values:
6417.705/18 = 356.539

The last step is to take the square root:
√356.539 = 18.882

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