Question

Power plants can emit levels of pollution that can lower air quality. For this reason, it...

Power plants can emit levels of pollution that can lower air quality. For this reason, it is important to monitor the levels of pollution they produce. Investigators measured dust emissions, in milligrams per cubic meter, at four power plants. Thirty measurements were taken for each plant. The sample means and standard deviations are presented in the table. Can you conclude there are differences among the mean emission levels at significance level 0.05?

Plant Mean Standard Deviation Sample Size
A 211.50 24.85 30
B 214.00 35.26 30
C 211.75 33.53 30
D 236.08 23.09 30

Homework Answers

Answer #1

from above data:

Group ni i S2i ni*(Xi-Xgrand)2 (ni-1)*S2i
A 30 211.5 617.523 1400.492 17908.15
B 30 214 1243.268 563.117 36054.76
C 30 211.75 1124.261 1299.879 32603.57
D 30 236.08 533.148 9449.213 15461.29
grand mean= 218.3325 12712.700 102027.77
SSTr SSE
Source SS df MS F Fcrit
between 12712.70 3.000 4237.5668 4.82 2.683
within 102027.77 116.000 879.5498
total 114740.47 119.0000

as test statistic Falls above critical value we reject null hypothesis

therefore we have sufficient evidenec to conclude that there are differences among the mean emission levels at significance level 0.05 .

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