Define normal distribution. What are the main chracteristics of normal distribution? Extruded plastic rods are automatically cut into length 5 inches. Actul length are normally distributed about a mean of  5 inches and their standard deviation is 0.05 inches. (i) What propotion of rods exceed tolerance limits of 4.9 inches to 5.1 inches? (ii) Proportion of rods having tolerance rod which is greater than 6.5 inches.