Answer:
Given that the maximum age of the textbook is 7.9 years and the minimum age of the textbook is 1.3 years.
Using the range rule, the standard deviation is estimated as,
S≈maximum−minimum/4
=7.9−1.3/4
=1.65
The required value of the approximate standard deviation is 1.65.
X = 5
more words because it wont send ;-;
Using the z-distribution, it is found that the smallest sample size required is given by:
B) 7 vehicles.
<h3>What is the margin of error for a z-distribution confidence interval?</h3>
It is given by:

In which:
is the population standard deviation.
In this problem, we have a 90% confidence level, hence
, z is the value of Z that has a p-value of
, so the critical value is z = 1.645.
The margin of error and the population standard deviation are given by, respectively:
.
Then, we solve for n to find the needed sample size.






Rounding up, 7 vehicles have to be sampled, hence option B is correct.
More can be learned about the z-distribution at brainly.com/question/25890103