After the cause and effect diagram has been completed, data needs to be collected to determine which potential causes are important. Pareto diagrams and check sheets are very effective in establishing the importance of the potential causes.
Many folks are under the mistaken belief that data oriented problem solving can be accomplished by collecting data on a problem, analyzing the results and deciding the correct solution. Once data is collected and analyzed, new questions often arise so another data collection and analysis iteration is necessary. In addition, many problems can have more than 1 root cause. Data collected investigating one potential cause may not address other important potential causes. Thus, several potential causes need to be studied using the data collection and analysis process.