Here's a solution that employs a tabularx
environment, to allow automatic line-wrapping in the headers of columns 4 and 7. A centered version of the X
column type is used for these two columns.

\documentclass[11pt,a4paper,titlepage]{article}
\usepackage{booktabs,tabularx,ragged2e,caption}
\newcolumntype{C}{>{\Centering\arraybackslash}X} % centered version of 'X' col.
\begin{document}
\begin{table}[!htbp]
\captionsetup{skip=0.333\baselineskip}
\caption{Confusion Matrix -- Logistic Regression.} \label{tab1}
\begin{tabularx}{\linewidth}{@{} l *{2}{rrC} @{}}
\toprule
& \multicolumn{3}{c}{Model 1}
& \multicolumn{3}{c}{Model 2} \\
& \multicolumn{3}{c}{(No Regularisation)}
& \multicolumn{3}{c}{(With Regularisation)}\\
\cmidrule(lr){2-4} \cmidrule(l){5-7}
& 0 & 1 & \% Correct Predictions
& 0 & 1 & \% Correct Predictions \\
\midrule
0 & 414 & 70 & 85.5 & 419 & 65 & 86.4\\
\addlinespace
1 & 67 & 420 & 86.2 & 58 & 429 & 88.1 \\
\midrule
\textbf{Average} &&& \textbf{85.9} &&& \textbf{87.3} \\
\bottomrule
\end{tabularx}
\end{table}
\end{document}
Addendum: If you don't need the table to span the full width of the textblock, a much more compact (and, in my opinion, better-looking) solution, which uses just the "standard" column types l
, c
, and r
, is available:

\documentclass[11pt,a4paper,titlepage]{article}
\usepackage{booktabs,caption}
\begin{document}
\begin{table}[!htbp]
\centering
\captionsetup{skip=0.333\baselineskip}
\caption{Confusion Matrix -- Logistic Regression.}
\label{tab1}
\begin{tabular}{@{} l *{2}{rrc} @{}}
\toprule
& \multicolumn{3}{c}{Model 1}
& \multicolumn{3}{c}{Model 2} \\
& \multicolumn{3}{c}{(No Regularisation)}
& \multicolumn{3}{c}{(With Regularisation)} \\
\cmidrule(lr){2-4} \cmidrule(l){5-7}
& 0 & 1 & \% Correct & 0 & 1 & \% Correct \\
&&& Predictions &&& Predictions \\
\midrule
0 & 414 & 70 & 85.5 & 419 & 65 & 86.4\\
\addlinespace
1 & 67 & 420 & 86.2 & 58 & 429 & 88.1 \\
\midrule
\textbf{Average} &&& \textbf{85.9} &&& \textbf{87.3} \\
\bottomrule
\end{tabular}
\end{table}
\end{document}