The physics literature contains many claims that ultrashort-lived unstable particles, such as a Higgs boson, have been observed. These claims are a matter of applying the 5σ-convention in particle physics. This paper, however, shows that by applying this 5σ-convention a category mistake is made, by which a pure reasoning is passed off as an observation. Not only are these two fundamentally different primitive notions at the very basis of science, but the pure reasoning in question is also weaker than an observation: what we have in each case is that the existence of the ultrashort-lived unstable particle is inferred to the best explanation, but that does absolutely not merit the stronger claim that the particle in question has been "observed". Consequently, the observational claims in question will thus have to be dismissed as overstatements. On a general note, this demonstrates that the empirical support for the Standard Model of particle physics is significantly less than hitherto thought.