In T 1872/08 which concerned inventive step and the non-obvious solution of a problem based on an advantageous effect demonstrated by means of comparative tests, the Opposition Division had not deemed the tests provided by the applicant (appellant) to be relevant because the tests had been made with one specific printer on one specific paper, both different from the paper and the printer used in example 18 of document (D9). The board stated that, according to the established jurisprudence of the boards of appeal, "in the case where comparative tests are chosen to demonstrate an inventive step with an improved effect over a claimed area, the nature of the comparison with the closest state of the art must be such that the effect is convincingly shown to have its origin in the distinguishing feature of the invention. For this purpose it may be necessary to modify the elements of comparison so that they differ only by such a distinguishing feature ..." (T 197/86, OJ 1989, 371, point 6.1.3 of the Reasons). The board concluded in T 1872/08 that the comparative tests provided sufficient evidence that the problem was solved.

In T 479/06 the board found that tests results cited by the proprietor to show that the problem was solved by the claimed solution and so established inventive step were not conclusive. It could not conclude on that basis that the technical problem had actually been solved, so the technical problem had to be redefined.

In T 568/11 the board stated that the technical problem needed to be reformulated. One of the arguments of the patent proprietor was that the additional differences between the compositions to be compared were so minimal that they would have no influence on the properties of the composition.

Concerning also an effect not attributable to the distinguishing of feature, in T 71/09, the mere comparison of the two compositions was insufficient to demonstrate that the alleged effect had been caused by the claimed solution or that this effect had been produced across the entire claimed area. Indeed, the improved resistance of hair dye to shampoos might be caused by other factors. Improved durability of hair dye had not been established for all the claimed compositions.

In T 1127/10 (hair treatment), since there was no experimental data in any of the examples in the patent, the appellant had submitted a document reporting on two series of comparative tests. The board, however, found that the document's description of the test procedure and analysis of the results were deficient and insufficiently informative to demonstrate plausibly that such an improvement had been achieved (see also T 1962/12 and T 383/13: comparative examples deficient – improvement not plausibly demonstrated). See also T 2371/13 (inventive step – plausibility of an effect alleged in the patent application – admissibility of comparative-test results filed after the filing date to demonstrate that effect).

The board in T 578/06, noting that the EPC does not require experimental proof for patentability, considered that the disclosure of experimental data or results in the application as filed and/or post-published evidence was not always required to establish that the claimed subject-matter solved the objective technical problem. This was particularly true where no substantiated doubt had been raised. In T 488/16 the board agreed with the appellant that it is not always required to include experimental data or results in an application (see T 578/06). It is, however, a conditio sine qua non that it is shown that the technical problem underlying the invention was at least plausibly solved at the filing date. If, as in the present case, the nature of the invention was such that it relied on a technical effect which was neither self-evident nor predictable nor based on a conclusive theoretical concept at least some technical evidence was required to show that a technical problem had indeed been solved.

The Enlarged Board stated in R 9/14 that the petitioner was mistaken in believing that the deciding board had committed a serious procedural violation by not informing it of the correct sequence to be followed in the problem-solution approach and in the way it had applied the substantive law. The submission of comparative-test results to prove an effect or improvement was part of the problem-solution approach when establishing the problem over the closest prior art that is effectively solved by the claimed subject-matter. The petitioner's specialist knowledge of patent law should have told it that. There could thus be no question of a "surprise" or infringement of the right to be heard.

In R 16/13 the board – ex officio – questioned the probative value of comparative examples relied upon by the patent proprietor although their conclusiveness for demonstrating a technical effect of the claimed invention had not been disputed by the opponent. The decision of the board under review was set aside.