A random sample of 15 workers from a vacuum flask assembly line was selected from a large number of such workers. Ivor Stopwatch, a work-study engineer, asked each of these workers to assemble a one-litre vacuum flask at their normal working speed. The times taken, in seconds, to complete these tasks are given below.
109.2 146.2 127.9 92.0 108.5 91.1 109.8 114.9 115.3 99.0 112.8 130.7 141.7 122.6 119.9
Assuming that this sample came from an underlying normal population, investigate the claim that the population mean assembly time is less than 2 minutes. (AEB)