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