But the study included conventional laparoscopy patients among the ones who had robot-assisted surgery, making it difficult to assess its conclusions.
Part of the problem may be because of the official secrecy that is welded to so much of the law, making it difficult to assess its use or effectiveness.
Furthermore, courses vary somewhat in assessment procedures, making it difficult to assess outcomes across training courses.
Journalists are also being turned away, making it difficult to assess the situation.
Records at Companies House show JCB Research has never filed accounts, making it difficult to assess what it does.
Communication and transports links have been disrupted by the storm making it difficult to assess damage and offer assistance.
The governor's office has not yet drafted his new legislation, making it difficult to assess in detail.
Amyas Morse, the auditor general, said the tactics were making it difficult to assess how well the department was managing projects.
Estonia quickly settled back into conservatism during the second half, creating little of note and making it difficult to assess the performance of England's defence.
But neither study compares the number of cases with the number of tires manufactured, making it difficult to assess the scope of the problem.
The practice of bearing extra weapons, being of questionable legality, is mostly done surreptitiously, making it difficult to assess how extensive it is.
