Question description
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-liter 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 120 seconds at a 1% significance.
