5. How does your blood pressure compare with that of others of your same gender? Check your systolic blood pressure against the appropriate histogram in part 3 or 4 to deter- mine whether your blood pressure is "normal" or whether it is unusually high or low.

Blood pressure is the pressure that the blood exerts against the walls of the arteries. When physicians or nurses measure your blood pressure, they take two readings. The systolic blood pressure is the pressure when the heart is contracting and therefore pumping. The diastolic blood pressure is the pressure in the arteries when the heart is relaxing. The diastolic blood pressure is always the lower of the two readings. Blood pressure varies from one person to another. It will also vary for a single individual from day to day and even within a given day. If your blood pressure is too high, it can lead to a stroke or a heart attack. If it is too low, blood will not get to your extremities and you may feel dizzy. Low blood pressure is usually not serious. So, what should your blood pressure be? A systolic blood pressure of 120 would be considered normal. One of 150 would be high. But since blood pressure varies with gender and increases with age, a better gauge of the relative standing of your blood pressure would be obtained by comparing it with the population of blood pressures of all persons of your gender and age in Canada. Of course, we cannot supply you with that data set, but we can show you a very large sample selected from it. The text web- site provides blood pressure data on 500 persons, 236 men and 264 women. This data was used as a case study in Data Analysis at the 2003 Annual Meeting of Statistical Society of Canada in Halifax. Entries for each person include that person's age and systolic blood pressure and several other variables of interest.