Usual and Unusual Values. In Exercises, consider a value to be unusual if its z score is less than −2 or greater than 2.

Earthquakes The Southern California Earthquake Data Center recorded magnitudes (Richter scale) of 10, 594 earthquakes in a recent year. The mean is 1.240 and the standard deviation is 0.578. Consider the magnitudes that are unusual. What are the magnitudes that separate the unusual earthquakes from those that are usual?

Answer

Step 1 of 3</p>

Given Mean(=1.24

SD()=0.578

Given Z score is less than −2 or greater than 2.

Step 2 of 3</p>

z=(x-)/

2=(x-1.24)/0.578

1.156=(x-1.24)

x=1.156+1.24=2.396