Key point
One idea
A link in your data does not prove one thing caused the other. It only says two things moved together in your sample.
Use causal words like “caused”, “improved”, or “reduced” only when your design supports it, such as a planned A/B test or a strong comparison.
Link versus cause
A link is a pattern. For example, students who used your timetable app more often also reported fewer missed classes.
A cause is a stronger claim. It says using the app led to fewer missed classes. That needs more evidence because other reasons may explain the pattern.