Which of the following is not a requirement for testing a claim about a mean with sigma known? choose the correct answer below. a. if, under a given assumption, there is an exceptionally small probability of getting sample results at least as extreme as the results that were obtained, we conclude that the assumption is probably not correct. b. if the sample results (or more extreme results) cannot easily occur when the null hypothesis is true, we explain the discrepancy between the assumption and the sample results by concluding that the assumption is true, so we do not reject the assumption. c. if the sample results (or more extreme results) can easily occur when the null hypothesis is true, we attribute the relatively small discrepancy between the assumption and the sample results to chance. d. a conclusion based on a confidence interval estimate will be the same as a conclusion based on a hypothesis test.