\cline in combination with \multirow not the same thickness as \cline without \multirow

Question

I have the following table:

\begin{table}[h]
\caption{\label{tab:}Model 1 - Model output}
\centering
\begin{tabular}{l|c|c|c|c|c|c|c}
    \hline
    & coefficient & Std. Error & t-value & p-value & 2,5\% & 97,5\% & R-sqr\\
    \cline{1-7}
    \rowcolor{gray!6}  (Intercept) & -0.094 & 0.002 & -59.912 & 0 & -0.097 & -0.091 & \multirow{3}{*}{0.192}\\
    \cline{1-7}
    cost & 0.017 & 0.001 & 19.805 & 0 & 0.015 & 0.018 & \\
    \cline{1-7}
    \rowcolor{gray!6}  lead\_cost & -0.010 & 0.001 & -13.762 & 0 & -0.012 & -0.009 & \\
    \hline
\end{tabular}  \end{table}

And I want all \clines to behave in the same way, precisely as the first and the third \cline. Why is my second \cline not behaving like the first and the third? Precisely, why is my second \cline not as thin as the first or the third and rather looks exactly like a \hline? I red other posts related to this without getting the proposed solutions.

Answer 1

In my opinion, it's not a good idea to place the value of the goodness-of-fit statistic in one of the regressor rows; better to place it on a line by itself.

I also don't think that the striping of alternate rows does much for legibility; I'd therefore get rid of the striping. To really improve legibility, I would (a) align the numbers in the data columns on their respective decimal markers and (b) omit all vertical rules and use fewer, but well-spaced, horizontal rules.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{booktabs,siunitx}
\newcolumntype{T}[1]{S[table-format=#1]}
\begin{document}

\begin{table}[h]
\caption{\label{tab:}Model 1 - Model output}
\centering
\begin{tabular}{@{} l T{-1.3} T{1.3} T{-2.3} c T{-1.3} T{-1.3} @{}}
    \toprule
    & {Coeff.} & {Std.\ Err.} & {$t$-value} & {$p$-value} & {2,5\%} & {97,5\%} \\
    \midrule
    (Intercept) & -0.094 & 0.002 & -59.912 & 0 & -0.097 & -0.091 \\    
    cost        &  0.017 & 0.001 &  19.805 & 0 &  0.015 &  0.018 \\    
    lead\_cost  & -0.010 & 0.001 & -13.762 & 0 & -0.012 & -0.009 \\
    \addlinespace
    R\textsuperscript{2} & 0.192\\ 
    \bottomrule
\end{tabular}  
\end{table}
\end{document}