The data that follow are observations collected from an experiment that
compared four treatments, \(\mathrm{A}, \mathrm{B}, \mathrm{C},\) and
\(\mathrm{D},\) within each of three blocks, using a randomized block design.
$$
\begin{array}{lrrrrrr}
&&&{\text { Treatment }} \\
\hline \text { Block } & \text { A } & \text { B } & \text { C } & \text { D }
& \text { Total } \\
\hline 1 & 6 & 10 & 8 & 9 & 33 \\
2 & 4 & 9 & 5 & 7 & 25 \\
3 & 12 & 15 & 14 & 14 & 55 \\
\hline \text { Total } & 22 & 34 & 27 & 30 & 113
\end{array}
$$
a. Do the data present sufficient evidence to indicate differences among the
treatment means? Test using
$$
\alpha=.05 .
$$
b. Do the data present sufficient evidence to indicate differences among the
block means? Test using \(\alpha=.05 .\)
c. Rank the four treatment means using Tukey's method of paired comparisons
with \(\alpha=.01\)
d. Find a \(95 \%\) confidence interval for the difference in means for
treatments \(\mathrm{A}\) and \(\mathrm{B}\).
e. Does it appear that the use of a randomized block design for this
experiment was justified? Explain.