Which of the following terms is odd one out?

Ishikawa diagram, Cause and effect diagram, and Fishbone diagram are all names for the same quality tool - a diagram used to identify root causes of problems. The Pareto diagram is a different tool altogether - it's a bar graph that displays the relative frequency or impact of problems to help prioritize improvement efforts. Therefore, Pareto diagram is the 'odd one out' as it serves a different purpose.