Final answer:
We need the mean gas mileage and the actual mileage of your car to calculate the correct z-score. Without this information, we cannot calculate it. However, a hypothetical z-score of -0.648 would not be considered unusually low mileage.
Step-by-step explanation:
To determine the z-score of your car's gas mileage, you will need the mean gas mileage (advertised claim) and the standard deviation for the model of car that you purchased, which is 1.19mpg. The z-score is calculated using the formula z = (X - μ) / σ,
where X is the observed value,
μ is the mean, and
σ is the standard deviation.
If the z-score is less than -2 or greater than 2, this would indicate that the car's mileage is unusually high or low, respectively.
Since the question mentioned a z-score of -0.648 (e), this would not be considered unusually low, because it's within the range of -2 to 2.
If we consider the example given that the observed value was less than the advertised claim, and using the standard deviation provided (1.19mpg) with a z-score of -0.648, this would lead to the conclusion that your car's mileage is not unusually low, since the absolute value of the z-score is less than 2.