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8
chap4/methodology.tex
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@ -272,13 +272,13 @@ keyboard?.''}
\\
& \textbf{H3} & Keys with lower actuation force are perceived as more satisfactory to type with than keys with higher actuation force. & \\
\\
& \textbf{H4} & An adjusted keyboard (non-uniform actuation forces) improves typing speed compared to standard keyboards (uniform actuation forces) (efficiency - speed).& \\
& \textbf{H4} & Differences in actuation force influence muscle activity while typing. & \\
\\
& \textbf{H5} & An adjusted keyboard decreases typing errors compared to standard keyboards (efficiency - error rate).& \\
& \textbf{H5} & An adjusted keyboard (non-uniform actuation forces) improves typing speed compared to standard keyboards (uniform actuation forces) (efficiency - speed).& \\
\\
& \textbf{H6} & An adjusted keyboard is perceived as more satisfactory to type with compared to standard keyboards. & \\
& \textbf{H6} & An adjusted keyboard decreases typing errors compared to standard keyboards (efficiency - error rate).& \\
\\
& \textbf{H7} & Differences in actuation force influence muscle activity while typing. & \\
& \textbf{H7} & An adjusted keyboard is perceived as more satisfactory to type with compared to standard keyboards. & \\
\end{longtable}
\subsubsection{Method}

6
chap5/results.tex
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@ -553,7 +553,7 @@ right term of the ``or'' questions. All sub-scales, pragmatic ($\alpha$ =
for Cronbach's alpha of $\alpha$ > 0.7 \cite{schrepp_ueq_handbook}. The mean
values for all responses of the \gls{UEQ-S} can be seen in Figure
\ref{fig:kcq_tkbs_res} and the individual responses to the additional question
(SATI) are presented in Figure \ref{fig:sati_tkbs_res}. We conducted
(SATI) are presented in Figure \ref{fig:res_tkbs_sati}. We conducted
\gls{rmANOVA}s for both sub-scales but found no statistically significant
variations for the pragmatic scale (F(3, 69) = 3.254, p = 0.06, post-hoc did not
reveal any tendencies) nor the hedonic scale (F(3, 69) = 0.425, p =
@ -598,7 +598,7 @@ observed in Tables \ref{tbl:res_tkbs_sati} and \ref{tbl:sum_tkbs_sati}.
with lower actuation force against keyboards with higher actuation
force. The first comparison of Aphrodite (50 g) and Nyx (35 g) was added,
because of the noticeable differences in the visual assessment of Figure
\ref{fig:sati_tkbs_res}}
\ref{fig:res_tkbs_sati}}
\label{tbl:res_tkbs_sati}
\end{table}
@ -629,7 +629,7 @@ observed in Tables \ref{tbl:res_tkbs_sati} and \ref{tbl:sum_tkbs_sati}.
\caption{Responses for the additional question \textit{``How satisfied have
you been with this keyboard?''} with the means for all participant
represented as horizontal lines}
\label{fig:sati_tkbs_res}
\label{fig:res_tkbs_sati}
\end{figure}

201
chap6/discussion.tex
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@ -36,12 +36,12 @@ that subjects typed a bit slower (< 3\%) on \textit{Athena (80 g)} compared to
\textit{Aphrodite (50 g)} and \textit{Hera (35 - 60 g)}. With the differences in
metrics that are commonly used to measure typing speed more closely related to
productivity (\gls{WPM}, \gls{AdjWPM}) and the trends that indicate a slight
difference in operating speed, we can accept our hypothesis that solely a
difference in actuation force has an impact on typing speed.
difference in operating speed, we can accept our hypothesis that a difference in
actuation force, at least indirectly, has an impact on typing speed.
\begin{phga_hyp}[\checkmark]
\begin{phga_hyp*}[1 $\rightarrow$ \cmark]
Actuation force has an impact on typing speed (efficiency - speed).
\end{phga_hyp}
\end{phga_hyp*}
% During our telephone interviews 76\% of respondents would have preferred a
% keyboard with lighter actuation force.
@ -65,13 +65,13 @@ fourteen of the twenty-four participants also reported, that \textit{Nyx's}
light actuation force was the reason for many accidental key presses. It further
stood out, that as shown in Figure \ref{fig:max_opc_ter}, \textit{Athena} was
the most accurate keyboard for 58\% of participants and also more accurate than
keyboard \textit{Own} for eleven of the subjects. This concludes, that a higher
actuation force has a positive impact on error rate.
keyboard \textit{Own} for eleven of the subjects. Overall, this concludes, that
a higher actuation force has a positive impact on error rate.
\begin{phga_hyp}[\checkmark]
\begin{phga_hyp*}[2 $\rightarrow$ \cmark]
Higher key actuation force decreases typing errors compared to lower key
actuation force (efficiency - error rate).
\end{phga_hyp}
\end{phga_hyp*}
\textbf{Impact of \gls{TER} on \gls{WPM}}
@ -81,19 +81,190 @@ this additional relation, we conducted a \gls{LRT} of fixed effects for our
linear mixed-effects model with two random effects (participant and first/second
typing test), fixed effect \gls{TER} and response variable \gls{WPM}. The
results of the \gls{LRT} ($\chi^2(1)$ = 110.44, p = 0.00000000000000022)
suggest, that the \gls{TER} indeed had an impact on \gls{WPM}. This could have
been, because every time an error was made, almost all participants decided to
correct it right away. With a higher error rate, this obviously leads to many
short interruptions and an increased number of characters that are not taken
into account when computing the \gls{WPM} metric.
together with the trends of lower \gls{WPM} with increasing \gls{TER}, visible
in Figure \ref{fig:reg_ter_wpm}, suggest, that the \gls{TER} indeed had an
impact on \gls{WPM}. This could have been, because every time an error was made,
almost all participants decided to correct it right away. With a higher error
rate, this obviously leads to many short interruptions and an increased number
of characters that are not taken into account when computing the \gls{WPM}
metric.
\begin{figure}[H]
\centering
\includegraphics[width=1.0\textwidth]{images/reg_ter_wpm}
\caption{Regression lines for the relation between \gls{TER} and \gls{WPM}.
The trends indicate a decrease in \gls{WPM} with rising \gls{TER} and
therefore the existence of a relation between the two metrics}
\label{fig:reg_ter_wpm}
\end{figure}
\subsection{Impact of Actuation Force on Satisfaction}
\label{sec:dis_sati}
We tried to narrow down the rather broad term ``satisfaction'' to individual
categories that we, with the information gathered through our literature review
and telephone interviews, defined as necessary for a positive user experience
while using a keyboard \cite{giese_sati}. We decided for the following metrics
to evaluate, whether or not a user experience with a keyboard that features
lighter actuation forces was more satisfactory:
\begin{table}[H]
\centering
\ra{1.0}
\small
\begin{tabular}{l}
$\rightarrow$ Pragmatic scale from the \glsfirst{UEQ-S} \\
$\rightarrow$ Score of the additional question \textit{``How satisfied have you been with this keyboard?''}\\
$\rightarrow$ Results of the \glsfirst{KCQ}\\
$\rightarrow$ Ranking of the keyboards during semi-structured interview\\
$\rightarrow$ Ratio of positive and negative feedback for each keyboard during semi-structured interview\\
\end{tabular}
\end{table}
\textbf{[\xmark] Pragmatic Scale (\gls{UEQ-S})}
As described in Section \ref{sec:res_ueqs}, we could not find statistically
significant differences for any of the test keyboards regarding the pragmatic
scale of the \gls{UEQ-S}. From visual assessment of the graph shown in Figure
\ref{fig:ueq_tkbs_res} we could conclude, that there is a slight trend towards a
more positive rating for keyboards that utilized keyswitches with higher
actuation forces than \textit{Nyx (35 g)}. This trend in the opposite direction
of our hypothesized outcome, that lighter actuation force leads to more user
satisfaction, could be due to the longer familiarization time required for
keyboards with very light actuation force \cite{gerard_keyswitch}.
\textbf{[\xmark] Additional Question of Satisfaction with Keyboard}
The results deduced from the additional question \textit{``How satisfied have
you been with this keyboard?''}, which could be answered on a \glsfirst{VAS}
from 0 to 100 after both tying tests with a keyboard, suggested that \textit{Nyx
(35 g)}, the keyboard with the lightest actuation force and also
\textit{Athena (80 g)} the keyboard with the highest actuation force, were rated
significantly worse than \textit{Aphrodite (50 g)}. Additionally, \textit{Hera
(35 - 60 g)}, the adjusted keyboard showed a trend towards a significantly
better rating than \textit{Nyx}. These results indicate, that neither of the
keyboards with extreme actuation forces were perceived as a overwhelmingly
pleasant keyboard to use during our typing tests. This is further supported by
the visualisation of the mean ratings in Figure \ref{fig:res_tkbs_sati} where
the average ratings for \textit{Aphrodite} and \textit{Hera} were approximately
10 points higher than those for \textit{Nyx} and \textit{Athena}.
\textbf{[\xmark] Keyboard Comfort Questionnaire (\gls{KCQ})}
For the \gls{KCQ} we found several statistically significant differences. For
questions related to effort or fatigue while operating a keyboard,
\textit{Athena (80 g)} received significantly lower ratings than the other test
keyboards. Additionally to the measured differences in error rates discussed in
Section \ref{sec:dis_error}, we discovered that participants also perceived the
accuracy of \textit{Athena (80 g)} and \textit{Aphrodite (50 g)} higher compared
to \textit{Nyx (35 g)}. Similarly to the results discussed in the last
paragraph, the scores of the two keyboards with extreme actuation forces,
\textit{Nyx (35 g)} and \textit{Athena (80 g)} fluctuated quite a bit and on
average those two keyboards scored lower than \textit{Aphrodite (50 g)} or
\textit{Hera (35 - 60 g)} (Figure \ref{fig:kcq_tkbs_res}). Thereby, these
results do not indicate a clear trend towards enhanced user experience when
using keyboards with lower actuation forces.
\textbf{[\xmark] Post Experiment Ranking of All Keyboards}
The ranks in terms of favored test keyboard, provided by all twenty-four
participants during the post-experiment semi-structured interview, can be
observed in Figure \ref{fig:tkbs_ranking}. The results further support the
tendencies towards keyboards with medium actuation forces, that we already
observed in the last couple paragraphs.
\begin{figure}[H]
\centering
\includegraphics[width=0.8\textwidth]{images/tkbs_ranking}
\caption{Rankings for only the test keyboards, gathered during the
post-experiment interview. It was possible to rank two or more keyboards the
same}
\label{fig:tkbs_ranking}
\end{figure}
\textbf{[\xmark] Ratio of Positive and Negative Feedback}
Lastly, we analysed all recordings of the post-experiment interviews and
categorized the feedback given for each keyboard into positive and negative
responses. We then calculated a ratio of these responses, which can be seen in
Figure \ref{fig:ratio_interview}, to evaluate preferences towards specific
keyboards, that could not be expressed by our participants through any other
supplied method during the experiment. Like all other factors we identified as
reasonable indicators for satisfaction, these ratios yielded, that neither
\textit{Athena (80 g)} nor \textit{Nyx (35 g)} received more positive than
negative feedback. It should be noted, that previous research has shown that
people tend to remember and process bad experiences more thorough than good
ones, which could be a reason for the increased number of negative feedback for
\textit{Nyx} and \textit{Athena} but would also indicate a worse experience with
those two keyboards \cite{baumeister_bad}.
\begin{figure}[H]
\centering
\includegraphics[width=0.9\textwidth]{images/ratio_interview}
\caption{The ration of $\frac{Positive Responses}{Negative Responses}$ during
the semi-structured interview for all test keyboards}
\label{fig:ratio_interview}
\end{figure}
\textbf{Conclusion}
Contrary to the responses of our preliminary telephone interview, where 76\% of
attendees preferred a keyboard with light actuation force, none of the factors
we defined as relevant for user satisfaction suggests, that keyboards with lower
actuation force are more satisfactory to use than keyboards with higher
actuation force. Therefore, we have to fully reject our hypothesis. We can
conclude thought, that keyboards with actuation forces in between those two
extremes (35 g / 80 g), are persistently perceived as more pleasant to use and
that ratings keyboards with extreme actuation forces are highly influenced by
personal preference, which is indicated by the high fluctuation of almost all
responses regarding our evaluated factors.
\begin{phga_hyp*}[3 $\rightarrow$ \xmark]
Keys with lower actuation force are perceived as more satisfactory to type
with than keys with higher actuation force.
\end{phga_hyp*}
\subsection{Impact of Actuation Force on Muscle Activity}
\label{sec:dis_emg}
In contrast to other studies that suggested, that actuation force has an impact
on muscle activity, we could not identify significant differences in terms of \%
of \glsfirst{MVC} for any of our \gls{EMG} measurements. Only a slight trend,
that \textit{Nyx (35 g)} produced the highest flexor \%\gls{MVC} for only 14\%
of participants, could be interpreted as anecdotal evidence towards our
hypothesis, that actuation force has an impact on muscle activity.
\subsection{Impact of an Adjusted Keyboard on Typing Speed, Error Rate and
Satisfaction}
\begin{phga_hyp*}[4 $\rightarrow$ \xmark]
Differences in actuation force influence muscle activity while typing.
\end{phga_hyp*}
%\subsection{Impact of an Adjusted Keyboard on Typing Speed, Error Rate and
% Satisfaction}
\subsection{Implications for the Adjusted Keyboard}
\label{sec:dis_hera}
As discussed in the previous sections, there were no statistically significant
differences in terms of satisfaction for any of the test keyboards, including
our adjusted keyboard \textit{Hera}. Still, the rather unconventional design
choice of non-uniform actuation forces across a keyboard did not negatively
influence the satisfaction compared to \textit{Aphrodite} which was often
perceived as equivalent to the participant's own keyboard. In fact,
\textit{Hera} was the keyboard with the most occurrences in the top three, tied
first place with \textit{Aphrodite} and was never ranked 4th place during the
post-experiment interview (Figure \ref{fig:tkbs_ranking}). Since \textit{Hera},
among others, utilized keyswitches with light actuation force (35 g), the
satisfaction could improve during prolonged usage, because of the longer
familiarization period required by keyboards with lighter actuation forces
\cite{gerard_keyswitch}. Interestingly, participant \textit{I3Z4XI7H} who
reported a currently present disease of the left arm and wrist (Syndrome Sudeck,
complex regional pain syndrome (CRPS)), ranked Hera 30 points higher than all
other keyboards. \textit{I3Z4XI7H} also reported in the post-experiment
interview, that \textit{Hera} was surprisingly pleasant to use and that pain was
significantly lower than with all other keyboards including
\textit{Own}. However, because of the nearly identical scores to
\textit{Aphrodite} we have to reject our hypothesis, that an adjusted keyboard
is more satisfactory to use than standard keyboards.
\begin{phga_hyp*}[7 $\rightarrow$ \xmark]
An adjusted keyboard is perceived as more satisfactory to type with compared to standard keyboards.
\end{phga_hyp*}

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22
ref_shelf.bib
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@ -923,3 +923,25 @@ volume = {13},
year = {2016},
pages = {67--75}
}
@article{giese_sati,
title={Defining consumer satisfaction},
author={Giese, Joan L and Cote, Joseph A},
journal={Academy of marketing science review},
volume={1},
number={1},
pages={1--22},
year={2000},
publisher={Vancouver}
}
@article{baumeister_bad,
title={Bad is stronger than good},
author={Baumeister, Roy F and Bratslavsky, Ellen and Finkenauer, Catrin and Vohs, Kathleen D},
journal={Review of general psychology},
volume={5},
number={4},
pages={323--370},
year={2001},
publisher={SAGE Publications Sage CA: Los Angeles, CA}
}

100
thesis.tex
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@ -22,7 +22,10 @@ openright]{scrartcl}
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@ -110,7 +113,96 @@ citecolor=red,
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@ -123,6 +215,8 @@ citecolor=red,
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@ -134,7 +228,9 @@ citecolor=red,
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