An article presents a study of the effect of the subbase thickness on the amount of surface deflection caused by aircraft landing on an airport runway. In six applications of a 160 kN load on a runway with a subbase thickness of 864 mm, the average surface deflection was 2.53 mm with a standard deviation of 0.090 mm. Find a 90% confidence interval for the mean deflection caused by a 160 kN load. Round the answers to three decimal places.

Respuesta :

Answer:

The 90% confidence interval is  [tex] 2.47<\mu < 2.59 [/tex]

Step-by-step explanation:

From the question we are told that

   The sample size is  n =  6

   The sample mean is  [tex]\= x = 2.53 \ mm[/tex]

   The standard deviation is  [tex]\sigma  =  0.090\ mm[/tex]

Given that the confidence level is 90% then the level of significance is  

        [tex]\alpha =  (100 - 90)\%[/tex]

=>     [tex]\alpha =  0.10 [/tex]

Generally from the normal distribution table the critical value  of  [tex]\frac{\alpha }{2}[/tex] is  

   [tex]Z_{\frac{\alpha }{2} } =  1.645 [/tex]

Generally the margin of error is mathematically represented as  

      [tex]E =1.645 *  \frac{0.090 }{\sqrt{6} }[/tex]

=>   [tex]E = 0.060 [/tex]

Generally 90% confidence interval is mathematically represented as  

      [tex]\= x -E <  \mu <  \=x  +E[/tex]

      [tex]2.53  -0.060 <\mu < 2.53  + 0.060[/tex]

=>   [tex] 2.47<\mu < 2.59 [/tex]