Oil Change

• You waited 3,467 miles before you changed oil (MacEwen, 2008).
• The mean people wait to change their oil is 3,258 miles (MacEwen, 2008).
• The standard deviation is 223 miles (MacEwen, 2008).

                             
Z= (3,467 – 3,258)/223                            The Normal Curve
Z-Score = .9372

Area below Z-Score = .17618 or 17.62%
Area above and below mean = .82382 or 82.38%
(.5+.32382=.82382)

Area between median and Z-Score = .32382 or 32.38%
(.5-.17618 = .32382)

This shows that 82.38% of all people wait 3,467 miles before having an oil change. Because this is such a high percent we believe that waiting this long to get an oil change is not too long.

MacEwen, B. (2008, spring). Psychology 261. Class lectures. University of Mary Washington.

Characteristics of the Normal Curve. Retrieved February, 4th, 2008 from http://math.youngzones.org/normal.html.

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