n a sample of seven​ cars, each car was tested for​ nitrogen-oxide emissions​ (in grams per​ mile) and the following results were​ obtained: 0.12​, 0.08​, 0.18​, 0.07​, 0.12​, 0.14​, 0.15 . Assuming that this sample is representative of the cars in​ use, construct a 98​% confidence interval estimate of the mean amount of​ nitrogen-oxide emissions for all cars. If the EPA requires that​ nitrogen-oxide emissions be less than 0.165 g divided by mi​, can we safely conclude that this requirement is being​ met?

Respuesta :

Answer:

(0.0772,0.1688)                                

Step-by-step explanation:

We are given the following data set:

0.12​, 0.08​, 0.18​, 0.07​, 0.12​, 0.14​, 0.15

n = 7

a) Formula:

[tex]\text{Standard Deviation} = \sqrt{\displaystyle\frac{\sum (x_i -\bar{x})^2}{n-1}}[/tex]  

where [tex]x_i[/tex] are data points, [tex]\bar{x}[/tex] is the mean and n is the number of observations.  

[tex]Mean = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}[/tex]

[tex]Mean =\displaystyle\frac{0.86}{7} = 0.123[/tex]

Sum of squares of differences = 0.000008163265305 + 0.001836734694 + 0.003265306122 + 0.002793877551 + 0.000008163265305 + 0.0002938775509 + 0.0007367346937 = 0.008942857142

[tex]S.D = \sqrt{\frac{0.008942857142}{6}} = 0.0386[/tex]

Confidence interval:

[tex]\mu \pm t_{critical}\frac{\sigma}{\sqrt{n}}[/tex]

Putting the values, we get,

[tex]t_{critical}\text{ at}~\alpha_{0.02}\text{ and degree of freedom 6} = \pm 3.142[/tex]

[tex]0.123 \pm 3.142(\frac{0.0386}{\sqrt{7}} ) = 0.123 \pm 0.0458 = (0.0772,0.1688)[/tex]

b) No, this requirement is not met because the interval contains value greater than 0.165 g as well.

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