Answer: 1022.75 kWh.
Step-by-step explanation:
Given: In one region, the September energy consumption levels for single-family homes are found to be normally distributed with a mean of 1050 kWh and a standard deviation of 218 kWh.
i.e. [tex]\mu=1050\ kWh[/tex] and [tex]\sigma=218\ kWh[/tex]
Let X denote energy consumption levels for random single-family homes and x be the energy consumption level for the 45th percentile.
Then, [tex]P(X<x)=0.45[/tex]
From z-table, [tex]P(z<-0.125)=0.45[/tex]
Also, [tex]z=\dfrac{x-\mu}{\sigma}[/tex]
[tex]\Rightarrow\ -0.125=\dfrac{x-1050}{218}\\\\\Rightarrow\ x=-0.125\times218+1050=1022.75[/tex]
Hence, the energy consumption level for the 45th percentile is 1022.75 kWh.
