Respuesta :
Answer:
a) The probability is the p-value of [tex]Z = \frac{X - 22.6}{5.2}[/tex], in which X is the gas mileage of the 2020 Honda Civic.
b) Your dad's truck is 1.65 standard deviations below the mean.
Step-by-step explanation:
Normal Probability Distribution
Problems of normal distributions can be solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the z-score of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Normal with mean 22.6 miles per gallon (mpg) and standard deviation 5.2 mpg.
This means that [tex]\mu = 22.6, \sigma = 5.2[/tex]
a. What proportion of vehicles have worse gas mileage than the 2020 Honda Civic?
This is the p-value of Z, given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{X - 22.6}{5.2}[/tex]
In which X is the gas mileage of the 2020 Honda Civic.
b. My dad has a truck that gets around 14 mpg. How many standard deviations from the mean is my dad's truck?
This is Z when X = 14. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{14 - 22.6}{5.2}[/tex]
[tex]Z = -1.65[/tex]
Your dad's truck is 1.65 standard deviations below the mean.
