For each of the following questions, DRAW the normal curvesand highlight the cor

Question

For each of the following questions, DRAW the normal curvesand highlight the corresponding areas. A certain brand of computer battery life is normallydistributed with an average of 6 hours before it needs to berecharged. The standard deviation is 1.2 hours. What percentage ofbatteries last: a. Between 3.6 and 8.4 hours. b. At most 7.2 hours. c. No less than 3.6 hours. For each of the following questions, DRAW the normal curvesand highlight the corresponding areas. A certain brand of computer battery life is normallydistributed with an average of 6 hours before it needs to berecharged. The standard deviation is 1.2 hours. What percentage ofbatteries last: a. Between 3.6 and 8.4 hours. b. At most 7.2 hours. c. No less than 3.6 hours.

Explanation / Answer

a. Between 3.6 and 8.4 hours.
P(3.6<X<8.4)=P((3.6-6)/1.2 <(X-)/ <(8.4-6)/1.2)
=P(-2<Z<2)
= 0.9544 (check normal table)

b. At most 7.2 hours.
P(X<7.2)=P(Z<(7.2-6)/1.2)
=P(Z<1)
= 0.8413 (check normal table)

c. No less than 3.6 hours.
P(X>3.6) = P(Z>(3.6-6)/1.2)
=P(Z>-2)
= 0.9772

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