Question

When Natalie moved from Nashville, TN to Philadelphia, PA, her average monthly water bill increased from $32 to $47. She is curious to know whether her TN or PA water bill is relatively more or less expensive, when compared to the distribution of water bills for each city. The mean and standard deviation for water bills in each city are shown in the table.

Answer 1

1$0.8$0.8​
2$0.625$0.625​
The mean monthly water bill in Nashville, TN is $30, with a standard deviation of $2.50. The z-score corresponding to Natalie's TN water bill of $32 is
z=x−μσ=32−302.5=0.8

The mean monthly water bill in Philadelphia, PA is $45, with a standard deviation of $3.20. The z-score corresponding to Natalie's PA water bill of $47 is
z=x−μσ=47−453.2=0.625