a firm ordered sacks of chemicals with a normal weight of 50kg. a random sample of 8 sacks was taken and it was found that the sample mean was 49.2kg...

a firm ordered sacks of chemicals with a normal weight of 50kg. a random sample of 8 sacks was taken and it was found that the sample mean was 49.2kg with standard deviation of 1.6kg. the firm wish to test whether the mean weight of the sample of sacks is significantly less than the normal weight , using a 5% level of  significance.