Clyde Cement wants to analyze a shipment of bags of cement. He knows the weight of the bags is normally distributed so he can use the standard normal distribution. He measures the weight of 600 randomly selected bags in the shipment. Next, he calculates the mean and standard deviation of their weights. The mean is 50 lbs and the standard deviation is 1.5 lbs. What percentage of the bags of cement will weigh less than 50 lbs.? 50 60 75 80

First, draw a normal distribution plot to use for the analysis of the data. Starting at the mean in the centre. Add one standard deviation for each interval to the right, and subtract one standard deviation for each interval to the right. See attached image. According to the empirical rule, 68% of data lies within one standard deviation of the mean, 95 % of the data is within two st. dev. and 99.7% of the data is within 3 st. dev. of the mean.

From the graph it can be deducted that half of the data will lie below 50, which makes it 50%.

An easier way of determining the answer is to use the definition of a mean. A mean is the number that,when all the data is placed in ascending order, lies right in the middle of all the data.