Answer:
a
The 95% confidence bounds is [tex] 145.80 < \mu < 158.19 [/tex]
b
It was not necessary to make any assumption about the shape of the travel time distribution
Step-by-step explanation:
From the question we are told that
The sample size is n = 30
The sample mean is [tex]\=x = 152[/tex]
The standard deviation is [tex]\sigma = 17.3 \ second[/tex]
From the question we are told the confidence level is 95% , hence the level of significance is
[tex]\alpha = (100 - 95 ) \%[/tex]
=> [tex]\alpha = 0.05[/tex]
Generally from the normal distribution table the critical value of [tex]\frac{\alpha }{2}[/tex] is
[tex]Z_{\frac{\alpha }{2} } = 1.96[/tex]
Generally the margin of error is mathematically represented as
[tex]E = Z_{\frac{\alpha }{2} } * \frac{\sigma }{\sqrt{n} }[/tex]
=> [tex]E = 1.96 * \frac{17.3 }{\sqrt{30} }[/tex]
=> [tex]E = 6.19 [/tex]
Generally 95% confidence bounds is mathematically represented as
[tex]\= x -E < \mu < \=x +E[/tex]
=> [tex]152 -6.19 < \mu < 152 -6.19[/tex]
=> [tex] 145.80 < \mu < 158.19 [/tex]
This 95% confidence bounds show that there is 95% confidence that the true mean lies within this bound hence there is it was not necessary to make any assumption about the shape of the travel time distribution
