## 4 Results: Manual Service Composition
### Manual Composition Problems and Overall Perception  
A user's technical profile had no significant effect on the number of problems, positive statements, and suggestions reported during manual service composition (\(t\)-test not significant). However, the number of conceptual problems encountered was significantly higher than that of the usability problems, (F (1, 46) = 20.24, \(p\) < 0.001), which reveals the complexity and challenging nature of manual composition (Table 4). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Category**} & \multicolumn{2}{c}{**Non-Programmers**} & \multicolumn{2}{c}{**Programmers**} \\ \cline{2-5}  & **M** & **SD** & **M** & **SD** \\ \hline Overall problems & 5.99 & 2.74 & 6.33 & 3.07 \\ \hline -Conceptual problems & **4.91** & **2.29** & 4.00 & 1.85 \\ \hline -Usability problems & 1.08 & 1.26 & 2.33 & 1.83 \\ \hline Positive statements & 3.00 & 2.67 & 3.33 & 2.62 \\ \hline Suggestions & 1.58 & 1.31 & 1.33 & 1.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Average number of problems, positive comments, and suggestions during manual service composition (per user; cells in grey color are significantly different). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Manual**} & \multicolumn{3}{c}{**Non-Programmers**} & \multicolumn{2}{c}{**Programmers**} \\ \cline{2-5}  & **Average Task** & **\# Users Who** & **Total** & **Average Task** & **\# Users Who** & **Total** \\
**Task** & **Completion** & **Completed** & **Correctness** & **Completion** & **Completed the** & **Correctness** \\
**Time (seconds)** & **the Tasks** & **Score** & **Time (Seconds)** & **Tasks** & **Score** \\ \hline
1. Conditional & & 10 & & 9 & \\ branching, operator and & (SD = 114.11) & 300 & (10 received substantial help) & 10 & (4 received some help, 2 received substantial help) & 19 \\
2. Binding & & 12 & & & \\ activity with an appropriate & 88 & (2 received some help, 1 received substantial help) & 32 & 93 & 12 (1 received some help) & 35 \\ \hline
3. Adding a & & 10 & & & \\ parallel branch ** (SD = 113.26)** & 288 & (6 received some help, 4 received substantial help) & 16 & 164 (SD = 57.11) & (6 received some help) & 21 \\
**Time (seconds)** & **(SD = 113.26)** & 4 received substantial help) & & & 7 \\
4. Specifying & 186 & 7 & 101 & (2 received some help, 1 received substantial help) & 17 \\
4. Specifying & 186 & (5 received some help) & 16 & (SD = 34.10) & 12 received substantial help) & 17 \\
5. Saving the & 22 & & & & \\ composition & (SD = 11.90) & 12 & 36 & 31 (SD = 13. Table 5 summarizes the main conceptual problems that non-programmers encountered during the manual service composition. In line with the performance results, the non-programmers reported that defining the conditional statement was the main source of difficulty, which supports our hypothesis H1b. This problem was also reported by the expert sample. Non-programmers were then hindered by complexity of workflow-based composition approach and their weak understanding of low-level terminology, but this was not a concern for the expert sample, arguably owing to their technical background. Instead, the expert sample was more critical about specifying data passing between services than the non-programmers, which is an interesting and unexpected finding. So, what makes these manual service composition tasks challenging to complete by non-programmers? Next, we delved into the factors that led to the emergence of the problems mentioned above. The most recurring problem highlighted by our participants revolved around expressing choice between two services using a conditional branch. A conditional branch is equivalent to creating an \"if (condition);... else...,\" statement using a traditional programming language. For non-programmers, the issue may be attributed to their weak understanding of the meanings of operators and parameters, and poor selection of the appropriate operator and parameters of the condition.