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

The standard deviation of this sample is 7.438

Step-by-step 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=(81+78+86+95)/(4)=85`

Substitute the values in the formula :

Standard deviation=
`\sqrt{((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