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Nezavi [6.7K]
2 years ago
9

A consumer group is testing camp stoves. To test the heating capacity of a stove, they measure the time required to bring 2 quar

ts of water from 50 degrees to boiling.
Two competing models are under consideration. Thirty-six stoves of each model were tested and the following results were obtained.
Model 1: mean time is 11.4 and standard deviation is2.5
Model 2: mean time is 9.9 and standard deviation is 3.0
Is there any difference between the performances of these two models? {use a .05 level of significance}. Find the p-value of the sample statistic and do a significance test.
Find a 95% confidence interval for the difference of the means.
Mathematics
1 answer:
kotykmax [81]2 years ago
4 0

Answer:

a

The decision rule  is  

Reject the null hypothesis

  The conclusion is  

There is sufficient evidence to show that there is a difference between the performances of these two models

b

The  95% confidence interval is  0.224   <  \mu_1 - \mu_2  < 2.776

Step-by-step explanation:

From the question we are told that

    The sample size is  n  =  36

    The first sample mean is  \= x_1   =  11.4

    The first standard deviation is  s_1 =  2.5

    The second sample mean is   \= x_2 =  9.9

     The second standard deviation is  s_2 =  3.0

      The level of significance is  \alpha  =  0.05

The null hypothesis is  H_o  :  \mu_1 - \mu_2 = 0

The alternative hypothesis is H_a :  \mu_1 - \mu_2 \ne 0

Generally the test statistics is mathematically represented as

      z =  \frac{ (\= x_1 - \= x_2 ) - (\mu_1 - \mu_2 ) }{ \sqrt{ \frac{s_1^2 }{n} + \frac{s_2^2 }{ n}  } }

=>    z =  \frac{ ( 11.4  - 9.9) - 0  }{ \sqrt{ \frac{2.5^2 }{36} + \frac{ 3^2 }{36 }  } }

=>     z = 2.3

From the z table  the area under the normal curve to the left corresponding to  2.3 is  

       P( Z >  2.3 ) =  0.010724

Generally the p-value is mathematically represented as

      p-value =  2 * P( Z >  2.3 )

=>    p-value  =  2 * 0.010724

=>    p-value  =  0.02

From the value obtained we see that  p-value  <  \alpha hence  

The decision rule  is  

Reject the null hypothesis

  The conclusion is  

There is sufficient evidence to show that there is a difference between the performances of these two models

Considering question b

From the question we are told the confidence level is  95% , hence the level of significance is    

      \alpha = (100 - 95 ) \%

=>   \alpha = 0.05

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

   Z_{\frac{\alpha }{2} } =  1.96

Generally the margin of error is mathematically represented as  

      E = Z_{\frac{\alpha }{2} } *  \sqrt{ \frac{s_1^2 }{n } + \frac{s_2^2}{n}}

 => E = 1.96  *    \sqrt{ \frac{2.5^2 }{ 36 } + \frac{ 3^2}{36}}

  => E = 1.276

Generally 95% confidence interval is mathematically represented as  

      ( \= x_1 - \= x_2) -E <  \mu_1 - \mu_2  < ( \= x_1 - \= x_2) + E

=>  ( 11.4 - 9.9 ) -1.276  <  \mu_1 - \mu_2 < ( 11.4 - 9.9 ) + 1.276

=>  0.224   <  \mu_1 - \mu_2  < 2.776

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