Question

The following observations were made on fracture toughness of a base plate of 18% nickel maraging steel:

69.5 71.9 72.6 73.1 73.3 73.5 75.5 75.7 76.0 76.1 76.2
76.2 77.0 77.9 78.1 79.6 79.6 79.9 80.1 82.2 83.7 94.5

Calculate a 99% CI for the standard deviation of the fracture toughness distribution.

Answer 1

From the given data, the following statistics are calculated:

n = 22

= 77.3727

s = 5.1570

= 0.01

df = 22 - 1 = 21

Confidence Interval:

Low Side:

From Table:

= 41.4009

Low Side:

High Side:

From Table:

= 8,0336

High Side:

Confidence Interval:

3.6728 < < 8.3378