Homework Help: statistics

Posted by karla on Sunday, April 17, 2011 at 5:04pm.

John drives to work each morning and the trip takes an average of  = 38 minutes. The distribution of driving times is approximately normal with a standard deviation of  = 5 minutes. For a randomly selected morning, what is the probability that John's drive to work will take between 36 and 40 minutes?

statistics - MathGuru, Monday, April 18, 2011 at 7:24pm
Use z-scores.
Find two z-scores using this formula:
z = (x - mean)/sd

Mean = 38
Sd = 5

Use 36 for x to determine first z-score.
Use 40 for x to determine second z-score.

Once you have both z-scores, check a z-table for the probability between the two scores.

I hope this will help get you started.

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