## 4 Results  
The first stage of the analysis was to compare the sales profitability results for both groups of enterprises. Table 1 below presents profitability ratios for the enterprises analysed. The differences between the two groups are clearly visible. Higher profitability ratios are achieved by units operating within purchasing groups. The next stage of the research was to evaluate the \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{3}{*}{
\begin{tabular}{c} **Financial** \\ **Indictors** \\ \end{tabular} } & \multicolumn{8}{c}{**Group**} \\ \cline{2-10}  & \multicolumn{4}{c}{**GPO (N = 46)**} & \multicolumn{4}{c}{**Independent**} & \multicolumn{4}{c}{**Enterprises (N = 25)**} & \multirow{2}{*}{\(p\)} \\ \cline{2-10}  & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{**Me**} & \multicolumn{2}{c}{**Std.**} & \multirow{2}{*}{**Min**} & \multirow{2}{*}{**Max**} & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{**Me**} & \multicolumn{2}{c}{**Std.**} & \multirow{2}{*}{**Min**} & \multirow{2}{*}{**Max**} \\  & & & & **Dev.** & & & & & Dev. & & \\ \hline ROS (return on & & & & & & & & & & \\ sales) [\%] & 4.52 & 4.21 & 2.92 & 1.08 & 14.05 & 2.01 & 1.16 & 0.91 & 0.99 & 8.20 & 0.0000 *** \\ \hline \hline \end{tabular}  
* \(p\) value was calculated using Mann-Whitney test, *** denotes statistical significance of difference between groups (respectively at level \(p<0.05;p<0.01\) and \(p<0.001\)); Source: author’s calculations and studies.  
\end{table} 
Table 1: Profitability ratios for the enterprises analysed (2016–2019). influence of purchasing groups on the profitability of enterprises. For this purpose, the greatest benefits obtained by enterprises operating in groups were presented. Then they were related to the appropriate assets and liabilities that had the significant impact on the level of profitability and financial liquidity, i.e., short-term receivables, short-term liabilities, inventories and the operating cycle. In the case of the purchasing groups, the greatest benefits they obtained through the economies of scale concerned:  
* reduction of costs in the item value of materials, goods at purchase price,
* attractive trade credit and the possibility of creating a competitive policy of managing receivables from customers. By obtaining a long period of payment of obligations towards the producer (the funds are paid into the account of the central unit), it is possible to extend the trade credits to the recipients. Today, when the prices of services and goods are at a similar level, an attractive trade loan allows retaining existing customers and gaining new ones,
* the use of additional discounts for early payment of liabilities. Very often companies receive an additional discount for a quick, early payment. This discount is particularly important for the company financial results and financial liquidity. It allows one to further reduce costs in the item value of goods sold at purchase price, which increases profits which, in the form of financial resources, improve financial liquidity. In a similar way, using a regression model, the existence and specificity of possible relationships between the cycles of receivables, liabilities and inventories, as well as belonging to GPO and the profitability ratio will be examined. The dependent variable of the regression model was profitability, and the independent variables: The length of the receivables, liabilities and inventories cycles and the dichotomous factor--Affiliation to the GPO. Additionally, interactions between membership in the GPO and the length of receivables, liabilities and inventories cycles were taken into account. The model explains quite well the variability of ROS among the surveyed companies (\(R^{2}\) = 64.9%).