At least one of the answers above is NOT correct (1 point) Periodically, the cou

Question

At least one of the answers above is NOT correct (1 point) Periodically, the county Water Department tests the drinking water of homeowners for contaminants such as lead and copper. The lead and copper levels in water specimens collected in 1998 for a sample of 10 residents of a subdevelopement of the county are shown below (mg/L 5.2 0.139 23 0.715 5.8 0.383 2.7 0.471 0.146 4.4 0.731 0.786 0.574 0.757 0.797 5.6 0.8 2.7 3.470 a 99% confidence interval for the mean lead level in water specmans or the subdevelopment (b) Construct a 99% confidence interval for the mean copper level in water specimans of the subdevelopment. SAS Note: You can earn partial credit on this problem ndows

Explanation / Answer

Solution :

(a) Given that lead as 5.2,2.3,5.8,2.7,5.6,4.4,3,0.8,2.7,3.4

=> mean x = 3.59

Sum of terms = 5.2 + 2.3 + 5.8 + 2.7 + 5.6 + 4.4 + 3 + 0.8 + 2.7 + 3.4 = 35.9
Number of terms = 10

Mean = Sum of terms/Number of terms
= 35.9/10
= 3.59

=> standard deviation s = 1.619

=> n = 10 ; df = n - 1 = 9

=> For 99% confidence interval , t = 3.250

=> the 99% confidence interval for the mean is x +/- t*s/sqrt(n)

=> 3.59 +/- 3.250*1.619/sqrt(10)

=> 1.9261 <= ? <= 5.2539

(b) Given that copper as 0.139,0.715,0.383,0.471,0.146,0.731,0.786,0.574,0.757,0.797

=> mean x = 0.5499

=> standard deviation s = 0.2553

=> n = 10 , df = n-1 = 9

=> For 99% confidence interval , t = 3.250

=> the 99% confidence interval for the mean is x +/- t*s/sqrt(n)

=> 0.5499 +/- 3.250*0.2553/sqrt(10)

=> 0.2875 <= ? <= 0.8123

  

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