Final answer:
The quality control manager at Sony employed systematic sampling to estimate manufacturing defects by selecting every 15th music CD following a set interval until reaching the desired sample size.
Step-by-step explanation:
The type of sampling used by the quality control manager at Sony to estimate the percentage of defects in a recent manufacturing batch of music CDs is systematic sampling. This approach involves selecting every 15th music CD beginning with the second one off the assembly line until a sample of 120 music CDs is reached. With systematic sampling, the first unit is selected at random, and the remaining units are chosen at regular intervals, which in this case is every 15th CD.
This method ensures that the sample is spread out over the entire batch and is often used when a population has a logical sequence. However, the quality of the estimates from systematic sampling can be poor if there are hidden patterns in the order of the population that coincide with the sampling interval.