In: Statistics and Probability
The average electricity usage per month for a 2000 ft2 house is 550 kWh and the standard deviation is 180 kWh.
What is the probability that a household will use more than 750 kWh per month?
It might help to sketch the distribution and put the important information on the graph.
z=? p(x>750)=?
Let x be the electricity usage per month.
x follows normal distribution with with mean ( µ ) = 550 kWh and standard deviation (σ) = 180 kWh
P(x>750)
z =
z = 1.11
Area less than z = 1.11 on z score is 0.8665
Therefore area greater than 1.11 is 1 - 0.8665 = 0.1335
P(x>750) = 0.1335