4. Hydrocarbons in the cab of an automobile were measured during trips on the New Jersey Turnpike and trips through the Lincoln Tunnel connecting New York and New Jersey. The concentrations (± standard deviations) of m- and p-xylene were: Turnpike: 31.4 ± 30.0 g/m3 (32 measurements) Tunnel: 52.9 ± 29.8 g/m3 (32 measurements) Do these results differ at the 95% confidence level?

Respuesta :

Answer:

No these these result do not differ at 95% confidence level  

Step-by-step explanation:

From the question we are told that

  The first concentrations is  [tex]c _1= 30.0 \ g/m^3[/tex]

      The second concentrations is  [tex]c _2 = 52.9 \ g/m^3[/tex]

  The first sample size is  [tex]n_1 =  32[/tex]

    The second sample size is  [tex]n_2 =  32[/tex]

   The  first standard deviation is [tex]\sigma_1 =  30.0 [/tex]

     The  first standard deviation is [tex]\sigma_1 =  29.0 [/tex]

The mean for  Turnpike is  [tex]\= x _1 = \frac{c_1}{n} = \frac{31.4}{32} = 0.98125[/tex]

The mean for   Tunnel is  [tex]\= x _2 = \frac{c_2}{n} = \frac{52.9}{32} = 1.6531[/tex]

The  null hypothesis is  [tex]H_o : \mu _1 - \mu_2 = 0[/tex]

The  alternative hypothesis is  [tex]H_a : \mu _1 - \mu_2 \ne 0[/tex]

Generally the test statistics is mathematically represented as

              [tex]t = \frac{\= x_1 - \= x_2}{ \sqrt{\frac{\sigma_1^2}{n_1} +\frac{\sigma_2^2}{n_2} }}[/tex]

         [tex]t = \frac{0.98125 - 1.6531}{ \sqrt{\frac{30^2}{32} +\frac{29^2}{32} }}[/tex]

        [tex]t = - 0.0899[/tex]

Generally the degree of freedom is mathematically represented as

     [tex]df = 32+ 32 - 2[/tex]

     [tex]df = 62[/tex]

The  significance [tex]\alpha[/tex]  is  evaluated as

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

=>   [tex]\alpha = (95 - 100 )\%[/tex]

=>   [tex]\alpha =0.05[/tex]

The  critical value  is evaluated as

      [tex]t_c = 2 * t_{0.05 , 62}[/tex]

From the student t- distribution table  

        [tex]t_{0.05, 62} = 1.67[/tex]

So

     [tex]t_c = 2 * 1.67[/tex]

=>  [tex]t_c = 3.34[/tex]

given that

       [tex]t_c > t[/tex] we fail to reject the null hypothesis so  this mean that the result do  not differ