Question

Our environment is very sensitive to the amount of ozone in the upper atmosphere. The level of ozone normally found is 7.77.7 parts/million (ppm). A researcher believes that the current ozone level is at an insufficient level. The mean of 840840 samples is 7.67.6 ppm. Assume a population standard deviation of 1.21.2. Does the data support the researcher's claim at the 0.10.1 level?

Step 1 of 6: State the null and alternative hypotheses.

step 2: find the test statistic

step 3: one tailed or two?

step 4: find the p value

step 5: level of significance

step 6: reject or fail to reject?

Answer 1

Ho :   µ =   7.7                  
Ha :   µ <   7.7       (Left tail test)          
                          
Level of Significance ,    α =    0.10                  
population std dev ,    σ =    1.2000                  
Sample Size ,   n =    840                  
Sample Mean,    x̅ =   7.6000                  
                          
'   '   '                  
                          
Standard Error , SE = σ/√n =   1.2000   / √    840   =   0.0414      
Z-test statistic= (x̅ - µ )/SE = (   7.600   -   7.7   ) /    0.0414   =   -2.42

p-Value   =   0.0079   [ Excel formula =NORMSDIST(z) ]              
Decision:   p-value<α, Reject null hypothesis

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THANKS

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