Tennis-Warehouse recently conducted a study of long distance phone calls made by
ID: 2505443 • Letter: T
Question
Tennis-Warehouse recently conducted a study of long distance phone calls made by its employees. The study showed that the length of the calls has a mean of 3.2 minutes, a standard deviation of 0.50 minutes and it follows the normal probability distribution.
(a) What portion of the calls was between 3.2 and 4 minutes?
(b) What portion of the calls was more than 4 minutes?
(c) What portion of the calls was between 4 and 4.5 minutes?
(d) What portion of the calls was between 3 and 4.5 minutes?
Need to know by 01/14/2014 8:30pm
Tennis-Warehouse recently conducted a study of long distance phone calls made by its employees. The study showed that the length of the calls has a mean of 3.2 minutes, a standard deviation of 0.50 minutes and it follows the normal probability distribution. What portion of the calls was between 3.2 and 4 minutes? What portion of the calls was more than 4 minutes? What portion of the calls was between 4 and 4.5 minutes? What portion of the calls was between 3 and 4.5 minutes?Explanation / Answer
(a) P(3.2 <X< 4) = P((3.2-3.2)/0.5 <(X-mean)/s <(4-3.2)/0.5 )
=P(0<Z<1.6) =0.4452 (from standard normal table)
(b) P(X>4) = P(Z>(4-3.2)/0.5)
=P(Z>1.6) =0.0548
(c) P(4 <X< 4.5) = P((4-3.2)/0.5<Z<(4.5-3.2)/0.5)
=P(1.6<Z<2.6) =0.0501
(d) P(3 <X< 4.5) = P((3-3.2)/0.5 <Z< (4.5-3.2)/0.5)
=P(-0.4<Z<2.6) = 0.6508
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