Answer: 0.9932
Step-by-step explanation:
Given : Mean : [tex]\mu=\$2.837\text{ per gallon }[/tex]
Standard deviation : [tex]\sigma = \$0.009\text{ per gallon}[/tex]
a) The formula for z -score :
[tex]z=\dfrac{x-\mu}{\dfrac{\sigma}{\sqrt{n}}}[/tex]
Sample size = 55
For x= $2.834 ,
[tex]z=\dfrac{2.834-2.837}{\dfrac{0.009}{\sqrt{55}}}\approx2.47[/tex]
The p-value = [tex]P(z<2.47)=[/tex]
[tex]0.9932443\approx0.9932[/tex]
Thus, the probability that the mean price per gallon is less than $2.834 is approximately 0.9932 .