Normal is synonymous with "usual" in all the physical sciences, and in much of non-human biology. It is thus normal for bears to sleep continuously during winter, for female spiders to eat the males that mate with them, and for rabbits to eat their own faeces.
In Human Biology normal is sometimes also defined as the usual. Thus the normal height of young men is the range of heights that includes 95% of men. It is also normal for newborn babies to sleep for more than 20 hours per day. It is similarly normal for non-pregnant young women to experience intermittent uterine bleeding.
In broad terms, the unusualness of a symptom is possibly the single most important determinant of whether a patient seeks medical advice or not. Thus, it is normal to feel short of breath after climbing 5 flights of stairs. But shortness of breath after brushing one's teeth is unusual, and therefore a persuasive reason to consult a physician.
This usage of the term normal is based on strict observation. It is rigorous and acultural. It dispassionately describes the species exactly as it is. The 95% probability limits constitute the most widely accepted normal range. This coincides with the internationally accepted limits of statistical significance (i.e. extra-normality is denoted by P<0.05). As such, it constitutes an indispensable tool in the diagnostic industry........
See that's what I said about it......
