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scientificComputing/statistics/lecture/statistics-chapter.tex

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\documentclass[12pt]{report}
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\title{\tr{Introduction to Scientific Computing}{Einf\"uhrung in die wissenschaftliche Datenverarbeitung}}
\author{Jan Benda\\Abteilung Neuroethologie\\[2ex]\includegraphics[width=0.3\textwidth]{UT_WBMW_Rot_RGB}}
\date{WS 15/16}
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\begin{document}
\include{statistics}
\end{document}
\end{document}
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\section{Statistics}
What is "a statistic"? % dt. Sch\"atzfunktion
\begin{definition}[statistic]
A statistic (singular) is a single measure of some attribute of a
sample (e.g., its arithmetic mean value). It is calculated by
applying a function (statistical algorithm) to the values of the
items of the sample, which are known together as a set of data.
\source{http://en.wikipedia.org/wiki/Statistic}
\end{definition}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{Data types}
\subsection{Nominal scale}
\begin{itemize}
\item Binary
\begin{itemize}
\item ``yes/no'',
\item ``true/false'',
\item ``success/failure'', etc.
\end{itemize}
\item Categorial
\begin{itemize}
\item cell type (``rod/cone/horizontal cell/bipolar cell/ganglion cell''),
\item blood type (``A/B/AB/0''),
\item parts of speech (``noun/veerb/preposition/article/...''),
\item taxonomic groups (``Coleoptera/Lepidoptera/Diptera/Hymenoptera''), etc.
\end{itemize}
\item Each observation/measurement/sample is put into one category
\item There is no reasonable order among the categories.\\
example: [rods, cones] vs. [cones, rods]
\item Statistics: mode, i.e. the most common item
\end{itemize}
\subsection{Ordinal scale}
\begin{itemize}
\item Like nominal scale, but with an order
\item Examples: ranks, ratings
\begin{itemize}
\item ``bad/ok/good'',
\item ``cold/warm/hot'',
\item ``young/old'', etc.
\end{itemize}
\item {\bf But:} there is no reasonable measure of {\em distance}
between the classes
\item Statistics: mode, median
\end{itemize}
\subsection{Interval scale}
\begin{itemize}
\item Quantitative/metric values
\item Reasonable measure of distance between values, but no absolute zero
\item Examples:
\begin{itemize}
\item Temperature in $^\circ$C ($20^\circ$C is not twice as hot as $10^\circ$C)
\item Direction measured in degrees from magnetic or true north
\end{itemize}
\item Statistics:
\begin{itemize}
\item Central tendency: mode, median, arithmetic mean
\item Dispersion: range, standard deviation
\end{itemize}
\end{itemize}
\subsection{Absolute/ratio scale}
\begin{itemize}
\item Like interval scale, but with absolute origin/zero
\item Examples:
\begin{itemize}
\item Temperature in $^\circ$K
\item Length, mass, duration, electric charge, ...
\item Plane angle, etc.
\item Count (e.g. number of spikes in response to a stimulus)
\end{itemize}
\item Statistics:
\begin{itemize}
\item Central tendency: mode, median, arithmetic, geometric, harmonic mean
\item Dispersion: range, standard deviation
\item Coefficient of variation (ratio standard deviation/mean)
\item All other statistical measures
\end{itemize}
\end{itemize}
\subsection{Data types}
\begin{itemize}
\item Data type selects
\begin{itemize}
\item statistics
\item type of plots (bar graph versus x-y plot)
\item correct tests
\end{itemize}
\item Scales exhibit increasing information content from nominal
to absolute.\\
Conversion ,,downwards'' is always possible
\item For example: size measured in meter (ratio scale) $\rightarrow$
categories ``small/medium/large'' (ordinal scale)
\end{itemize}
\subsection{Examples from neuroscience}
\begin{itemize}
\item {\bf absolute:}
\begin{itemize}
\item size of neuron/brain
\item length of axon
\item ion concentration
\item membrane potential
\item firing rate
\end{itemize}
\item {\bf interval:}
\begin{itemize}
\item edge orientation
\end{itemize}
\item {\bf ordinal:}
\begin{itemize}
\item stages of a disease
\item ratings
\end{itemize}
\item {\bf nominal:}
\begin{itemize}
\item cell type
\item odor
\item states of an ion channel
\end{itemize}
\end{itemize}