A study was conducted to monitor the emissions of a noxious substance from a che
ID: 3054075 • Letter: A
Question
A study was conducted to monitor the emissions of a noxious substance from a chemical plant and the concentration of the chemical at a location in close proximity to the plant at various times throughout the year. A total of 14 measurements were made. Computer output for the simple linear regression least-squares fit is provided. (Some entries have been omitted and replaced with **.)
Linear Fit
Concentration = 1.5429211 + 1.8247687 emissions
Summary of Fit
RSquare 0.793919
RSquare Adj 0.776745
Root Mean Square Error 1.513979
Mean of Response 8.810714
Observations (or Sum Wgts) 14
Analysis of Variance
Source DF Sum of Squares Mean Square FRatio
Model 1 105.96390 105.9639 46.2294
Error 12 27.50559 2.29 Prob >F
C. Total 13 133.46949 <.0001
Parameter Estimates
Term Estimate Std Error t Ratio Prob>|t|
Intercept 1.5429211 1.142937 **** 0.2019
Emissions 1.8247687 0.268379 **** <.0001
A) Calculate the 95% confidence interval for slope coefficient B1
B) Do the hypothesis test H0: B1 =0 against Ha: B1 ? 0. (State the null and alternative hypothesis, test statistics, p-value and conclusion, please also provide the meaning of this conclusion.)
Explanation / Answer
Answer below:
A.
95% CI is :
Coeff +/- t*SE
= 1.8247687 +/- t* 0.268379
t value for 95% CI at df = 13 is 2.160
So, = 1.8247687 +/- 2.160* 0.268379
=1.2451 to 2.4045
B.
Its already done in the regression table.
Null and alternate hypo:
Ho: B1=0
Ha: B1!=0
Test stat = (Estimate-0)/SE = 1.8247687/.268379 = 6.7992
Since our test statistic is more than the critical t of 2.160 we have the
fact the we reject Ho and conclude that Emissions is statistically significant
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