In one region, the Septemberenergy consumption levels for single-family homes ar

Question

In one region, the Septemberenergy consumption levels for single-family homes are found to benormally distributed with a mean of 1050 kWh and a standarddeviation of 218 kWh. For a randomly selected home, find theprobability that the September energy consumption level is between1100 kWh and 1225 kWh. 12% of American households nolonger have a landline telephone, instead relying solely on a cellphone. If 8American households are randomly selected, what isthe probability that 2 or 3 of them do not have alandline telephone? In one region, the Septemberenergy consumption levels for single-family homes are found to benormally distributed with a mean of 1050 kWh and a standarddeviation of 218 kWh. For a randomly selected home, find theprobability that the September energy consumption level is between1100 kWh and 1225 kWh. 12% of American households nolonger have a landline telephone, instead relying solely on a cellphone. If 8American households are randomly selected, what isthe probability that 2 or 3 of them do not have alandline telephone?

Explanation / Answer

=1050 =218 P(1100<X<1225)=? we convert to std normal variable Z where z=x-/ =x-1050/218 thus P(1100<X<1225)=P(1100-1050/218<Z<1225-1050/218)          =P(0.2294<Z<0.8028)         =P(Z<0.8028)-P(Z<0.2294) using std. normal table we get P(1100<X<1225)=0.7967-0.5910=0.2057

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