Comparing data characteristics to theoretical properties: Observe the distribution of the data set:Do approximately 2/3 of the observations lie within mean ±1 standard deviation?Do approximately 80% of the observations lie within mean ±1.28 standard deviations?Do approximately 95% of the observations lie within mean ±2 standard deviations? Evaluate normal probability plot:Is the normal probability plot approximately linear (i.e. a straight line) with positive slope?