Question 364036
The standard normal curve has a few neat properties that make it convenient to use. (Aside from its being a benchmark for all computations involving any normal distribution.)  Among them are its zero mean and standard deviation of 1.  There is the 68-95-99.7 rule, which says that 68% of the observations fall between -1 and 1 (within 1 standard deviation of the mean of 0), 95% fall between -2 and 2 (within 2 standard deviations of the mean) and 99.7% fall between -3 and 3 (within 3 standard deviations of the mean).  Thus, P(-1 < z <1) = 0.68,  P(-2 < z< 2) = 0.95, and P(-3 < z <3) = 0.997.  You don't need a standard normal table for these. =)