A manufacturer of automobiles developed a method of measuring noise in their engines. The method was calibrated to human responses. Engines that measured greater than 7.0 were considered noisy, and engines that measured less than 6.0 were considered quiet. Control charts on this measurement indicated that the engines currently being produced had greater noise levels than those that had been assembled in the previous month. The cause of the increase in noise was suspected to be found in the crank or the balancer since both of these components contained gears.

The following experimental plan was developed to isolate the source of the noise:

1. Eight engines were obtained for the study. Four of the engines were noisy (greater than 7.0) and four of the engines were quiet (less than 6.0).
2. The eight engines were disassembled into three components: the balancer, the crankshaft, and the rest of the engine (the block).
The three components thus become the three factors in the study. Each factor was studied at two levels, quiet or noisy. The level was based on whether the component came from a noisy or quiet engine. For each component, four were labeled noisy and four were labeled quiet.
3. Eight engines were reassembled using the 23 factorial design.
Each of the three components of the engines was randomly selected from the noisy or quiet group according to the design.
Each engine was then tested for noise. The results are shown in the table.
Analyze the data and determine which components cause the noise problem.

Transcribed Image Text:

Test Test order Balancer Crankshaft Block Measured noise 1 3 Noisy Noisy Noisy 8.5 234 569 5 Quiet Noisy Noisy 9.0 1 Noisy Quiet Noisy 5.9 6 Quiet Quiet Noisy 5.2 2 Noisy Noisy Quiet 10.3 8 Quiet Noisy Quiet 10.5 4 Noisy Quiet Quiet 7.2 8 7 Quiet Quiet Quiet 5.7