Posted by mary on .
Please help, very lost
Eric has computed that it takes an average (mean) of 17 minutes with a standard deviation of 3 minutes to drive from home, park the car, and walk to his job.
One day it took Eric 21 minutes to get to work. You would use the formula for transforming a raw score in a sample into a zscore to determine how many standard deviations the raw score represents.
Since his "score" is 21, you would subtract the mean of 17 from 21 and divide that result (4) by the standard deviation of 3.
The zscore of 1.33 tells you that Ericâ€™s time to get to work is 1.33 standard deviations from the mean.
Another day, it took Eric only 12 minutes to get to work. Using the same formula, determine the z value. Is it positive or negative? Explain why it should be positive or negative. It is simple what happens when you subtract 21 from 21.
On a different day, it took Eric 17 minutes to get from home to work. What is the z value? Why should you expect this result even before you did the calculation?

psychology (statistics) 
PsyDAG,
Please only post your questions once. Repeating posts will not get a quicker response. In addition, it wastes our time looking over reposts that have already been answered in another post. Thank you.