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\title{Stephen Erickson}
\date{\emph{Curriculum Vitae \\ rev.~\today}}
\author{4136 Grand View Boulevard \#17 \\
Los Angeles, California 90066--5222 \\
(310) 737-9696 \\
erickson@stat.ucla.edu}

\begin{document}

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{\bf Statistics 10 \\
Fall 2001 \\
Prof. Dinov \\
HW \#1 Solutions}

\subsubsection*{HW 1.1}

{\bf Study 1} \\
Treatment: subject weights. \\
Response: score on comprehensive exam. \\
This is an \emph{uncontrolled experiment}, because there is no feasible
way the researcher could randomly assign subjects to different treatment
groups, yet the study is not strictly observational.
There is no blocking in this study. 

{\bf Study 2} \\
Treatment: baking temperature. \\
Response: impact strength. \\
This is an \emph{experiment}.  For blinding purposes, the lab which evaluates
impact strength should not know the baking temperatures.
There is no blocking in this study.

{\bf Study 3} \\
Treatment: use of diagnostic machine. \\
Response: service time. \\
This is an \emph{experiment}.  For blinding purposes, an independent observer 
should record service times and, if possible, not be allowed to know whether 
the diagnostic equipment is being used.  The experiment would be better
designed if the order of repairs using the machine vs.~not using the
machine were randomized.
The use of two mechanics of different levels of experiences introduces 
blocking.

{\bf Study 4}\\
Treatment: student gender. \\
Response: grade on exams. \\
This is an \emph{uncontrolled experiment}.  As in study~1, there is no feasible
way of randomly assigning treatment groups.
If separate scores were available for each of the 10 exams, that would
represent a form of blocking.

\newpage

\subsubsection*{HW 1.2}

{\footnotesize \verbatiminput{stemleaf.txt}}

\begin{tabular}{r|l}
           Mean & 42.66 \\
                & \\
            Min & 32 \\
 Lower quartile & 38 \\
         Median & 41 \\
 Upper quartile & 47 \\
            Max & 68
\end{tabular}

\epsfig{width=2.5in,file=boxplot}

The data are right-skewed, which means that there are a small number of days
in which a very large number of parking tickets are given out.

The median number of parking tickets is 41.  The minimum number of 32 is only
9 tickets less than the median, while the maximum number of 68 is 27 tickets
more than the median.

The mean number of tickets (42.66) is larger than the median.  This is
typical of right-skewed distributions.

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