Posted by Nathan on .
The time required for a citizen to complete the 2000 U.S. Census "Long" form is normally distributed with a mean of 40 minutes and a standard deviation of 10 minutes. what proportion of the citizens will require less than 1 hour?
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Is there anyway you could explain that to me so I can understand it?
1 hour is 20 minutes = 2 standard deviations away from the mean. Your stats book should have a cumulative normal distribution table. Look up 2.0 in the table. I get .9772. Ergo, 97.72% will require less than an hour.