Monthly water bills for a city have a mean of $108.43 and a standard deviation of $36.98. find the probability that a randomly selected bill will have an amount greater than $173, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

The probability that a randomly selected bill will have an amount greater than $173 is 0.04006.    

No, a bill with $173 can not be considered unusual.

Step-by-step explanation:

We have been given that monthly water bills for a city have a mean of $108.43 and a standard deviation of $36.98.

First of all, we will find z-score of data point 173 using z-score formula.

, where,

Substitute the given values:

Now, we will use formula as:

From normal distribution table, we will get:

Therefore, the probability that a randomly selected bill will have an amount greater than $173 would be 0.04006 or 4.001%.

Since z-scores lower than -1.96 or higher than 1.96 are considered unusual. As the bill with size $173 has z-score of 1.75, therefore, a bill with size $173 can not be considered unusual.

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