1. A new strain of nitrogen fixing, root nodule bacteria (genus Rhizobium) was produced by microbial genetic engineers at UNT. An experiment was designed to test whether or not the new strain could fix nitrogen at more rapid rates than controls. The following data were collected (ng nitrogen fixed / mg bacteria / hour) under identical conditions in the laboratory.


Controls 7.8 7.9 8.0 8.4 8.6 8.8 9.0 9.2 9.8 10.4 11.4 11.8
Strain X7 8.2 8.6 9.8 10.4 10.8 12.4 12.5 12.8
a) Determine the indicated descriptive statistics for each group.
Table II – 34. Descriptive statistics for nitrogen fixation rates of control and experimental strains of bacteria.

N 
Mean 
SS 
SD 
S^{2} 
Control Strain X – 7 
12 8 




Please state appropriate null and alternate hypothesis for each analysis. (2 pts)
Now, we need to test whether the assumptions are satisfied:
b) Using R code to determine whether samples from control and Strain X7 follow normal distributions.
C) Hand calculation to determine if the variances are significantly different (α = 0.05).
d) Based on the tests in (c) and (d), choose an appropriate test to determine whether the mean fixation rates of control and Strain X7 are different at α =0.05.
e) Construct a confidence interval of the difference of the two mean rates.
f) Determine if mean fixation rates of strain X7 was at least 1 unit greater than controls at α =0.05.
g) Provide a R code and output for (c) and (d) and find out the pvalues from your output.
Subject  Mathematics 
Due By (Pacific Time)  10/31/2013 11:00 pm 
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