Need help asap with standard deviation :-)

Question

 

In a factory, the packets of sweets produced are supposed to contain 1kg each. It has been found that the weights are normally distributed with mean 1.01kg and standard deviation 0.009kg. Find, to 1 decimal place, the percentage of packets above the nominal 1kg weight.

Answer 1

The z score is (1-1.01)/0.009=-10/9=-1.1111, the number of SD's from the mean. The ND table gives us 0.1333 for this value of z, which is about 13.3%. This is the percentage of packets below 1kg, so 86.7% are above the nominal weight.