Question

Strength tests on four batches of concrete show them to fail at 81, 78, 86, and 95 ksi. The standard deviation of this sample is most nearly:

Answer 1

Answer:

The standard deviation of this sample is 7.438

Explanation:

We are given that Strength tests on four batches of concrete show them to fail at 81, 78, 86, and 95 ksi.

Data: 81, 78, 86, and 95

We are supposed to find standard deviation of this sample

Formula :$\sqrt{\frac{(x-\bar{x})^2}{n-1}}$

n = 4

$\bar x=\frac{81+78+86+95}{4}=85$

Substitute the values in the formula :

Standard deviation=$\sqrt{\frac{(81-85)^2+(78-85)^2+(86-85)^2+(95-85)^2}{4-1}}$

Standard deviation=7.438

Hence The standard deviation of this sample is 7.438