Null hypothesis significance testing has been under attack in recent years, partly owing to the arbitrary nature of setting α (the decision-making threshold and probability of Type I error) at a constant value, usually 0.05. If the goal of null hypothesis testing is to present conclusions in which we have the highest possible confidence, then the only logical decision-making threshold is the value that minimizes the probability (or occasionally, cost) of making errors. Setting α to minimize the combination of Type I and Type II error at a critical effect size can easily be accomplished for traditional statistical tests by calculating the α associated with the minimum average of α and β at the critical effect size. This technique also has the flexibility to incorporate prior probabilities of null and alternate hypotheses and/or relative costs of Type I and Type II errors, if known. Using an optimal α results in stronger scientific inferences because it estimates and minimizes both Type I errors and relevant Type II errors for a test. It also results in greater transparency concerning assumptions about relevant effect size(s) and the relative costs of Type I and II errors. By contrast, the use of α = 0.05 results in arbitrary decisions about what effect sizes will likely be considered significant, if real, and results in arbitrary amounts of Type II error for meaningful potential effect sizes. We cannot identify a rationale for continuing to arbitrarily use α = 0.05 for null hypothesis significance tests in any field, when it is possible to determine an optimal α.

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Many animals that live in northern climates enter a state of prolonged dormancy during winter. These animals possess a suite of physiological and behavioural adaptations that minimize threats to survival while overwintering. There are three major threats to overwintering survival: metabolic and respiratory acidosis, freezing, and predation. Selection of hibernation sites should minimize these threats. We monitored dissolved oxygen, water depth, and temperature at overwintering locations of Blanding’s Turtles ( Emydoidea blandingii (Holbrook, 1838)) and at stations located haphazardly in six different habitat types over two winters in Algonquin Park, Ontario, Canada. Water depth and dissolved oxygen in overwintering sites used by turtles were similar to those measured at haphazard stations. In contrast, estimated turtle body temperatures (~0 °C) were significantly lower and less variable than water temperatures measured at haphazard stations. These data and those reported elsewhere suggest that there are two alternatives for selection of suitable hibernacula by anoxia tolerant turtles. In areas where there is periodic access to aerial oxygen, turtles select sites where ice cover may not be present for the entire winter, but in areas where ice cover restricts access to air, turtles select sites where water temperatures are close to 0 °C.