Eruptions of the Old Faithful geyser have duration times with a mean of 245.0 sec and a standard deviation of 36.4 sec (based on Data Set 15 in Appendix B). One eruption had a duration time of 110 sec.

a. What is the difference between a duration time of 110 sec and the mean?

b. How many standard deviations is that (the difference found in part (a))?

c. Convert the duration time of 110 sec to a z score.

d. If we consider “usual” duration times to be those that convert to z scores between -2 and 2, is a duration time of 110 sec usual or unusual?