66. A deficiency of the trace element selenium in the diet can negatively impact growth, immunity, muscle and neuromuscular function, and fertility. The introduction of selenium supplements to dairy cows is justified when pastures have low selenium levels. Authors of the paper “Effects of Short-

Term Supplementation with Selenised Yeast on Milk Production and Composition of Lactating Cows”

(Australian J. of Dairy Tech., 2004: 199–203) supplied the following data on milk selenium concentration (mg/L) for a sample of cows given a selenium supplement and a control sample given no supplement, both initially and after a 9-day period.

Obs Init Se Init Cont Final Se Final Cont 1 11.4 9.1 138.3 9.3 2 9.6 8.7 104.0 8.8 3 10.1 9.7 96.4 8.8 4 8.5 10.8 89.0 10.1 5 10.3 10.9 88.0 9.6 6 10.6 10.6 103.8 8.6 7 11.8 10.1 147.3 10.4 8 9.8 12.3 97.1 12.4 9 10.9 8.8 172.6 9.3 10 10.3 10.4 146.3 9.5 11 10.2 10.9 99.0 8.4 12 11.4 10.4 122.3 8.7 13 9.2 11.6 103.0 12.5 14 10.6 10.9 117.8 9.1 15 10.8 121.5 16 8.2 93.0

a. Do the initial Se concentrations for the supplement and control samples appear to be similar? Use various techniques from this chapter to summarize the data and answer the question posed.

b. Again use methods from this chapter to summarize the data and then describe how the final Se concentration values in the treatment group differ from those in the control group.