The check/study phase should be reviewing the results of the experiment done in the Do the experiment phase. "Checking" how things are going during the experiment makes sense but that isn't the check/study phase of PDSA .
For example, you don't want to pay no attention during the experiment and then look at the data and discover the data shows obvious signs the operational definitions were not clear, or the process is providing very bad results. So you need to have those doing the experiment paying attention daily.
Remember one key to using the PDSA cycle is to turn through the whole cycle quickly. Daily would be exceptionally quick. Moving through the whole cycle in 2-6 weeks is more normal. Organizations successful using PDSA will quickly turn the cycle 4+ times for a specific effort (often the 2nd, 3rd... times through are much faster than the first time through).
More on how to use the PDSA well:
- Resources for Using the PDSA Cycle to Improve Results
- The Improvement Guide is a book anyone using PDSA should read and consult frequently as a resource (blog post on the book)
- Keys to the Effective Use of the PDSA Improvement Cycle