The distribution of carbon monoxide (CO) emissions for a certain kind of car is

Question

The distribution of carbon monoxide (CO) emissions for a certain kind of car is approximately Normal and varies with mean of 2.9 g/mi and standard deviation of 0.4 g/mi. Use the NormalCDF and InvNorm commands on the calculator to answer the following.

6) What are the values of the first quartile and third quartile of CO emissions? Q1 = Answer

g/mi Q3 = Answer g/mi (Round to the nearest tenth.)

A company has 80 of these cars in its fleet. Let y-bar represent the mean CO level for the company's fleet.

7) Verify the appropriate assumptions, conditions, and model for the sampling distribution of y-bar before proceeding:

Randomization condition: Answer
Independence assumption: Answer
10% condition: Answer
Large Enough Sample condition: Answer

Since the conditions are met, the CLT allows us to model the sampling distribution of y-bar with a Answer model, with = Answer g/mi and a standard deviation = Answer/Answer Answer g/mi. (Round to three decimal places.)

Explanation / Answer

6.

First, we get the z score from the given left tailed area. As          
          
Left tailed area =    0.25      
          
Then, using table or technology,          
          
z =    -0.67448975      

[Invnorm(0.25,0,1)]
          
As x = u + z * s,          
          
where          
          
u = mean =    2.9      
z = the critical z score =    -0.67448975      
s = standard deviation =    0.4      
          
Then          
          
x = Q1 =    2.6302041   [ANSWER, Q1]  

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First, we get the z score from the given left tailed area. As          
          
Left tailed area =    0.75      
          
Then, using table or technology,          
          
z =    0.67448975      
  
[Invnorm[0.75,0,1]
      
As x = u + z * s,          
          
where          
          
u = mean =    2.9      
z = the critical z score =    0.67448975      
s = standard deviation =    0.4      
          
Then          
          
x = Q3 =    3.1697959   [ANSWER, Q3]

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