Solar joint inspections. X-rays and lasers are used to inspect solder-joint defects on printed circuit boards

(PCBs). A particular manufacturer of laser-based inspection equipment claims that its product can inspect LO9 at least 10 solder joints per second, on average, when the joints are spaced .1 inch apart. The equipment was tested by a potential buyer on 48 different PCBs. In each case, the equipment was operated for exactly 1 second.

The numbers of solder joints inspected on each run are listed in the table on the next page.

10 9 10 10 11 9 12 8 8 9 6 10 7 10 11 9 9 13 9 10 11 10 12 8 9 9 9 7 12 6 9 10 10 8 7 9 11 12 10 0 10 11 12 9 7 9 9 10a. The potential buyer doubts the manufacturer’s claim.
Do you agree?
*b. Assume that the standard deviation of the number of solder joints inspected on each run is 1.2, and the true mean number of solder joints that can be inspected is really equal to 9.5. How likely is the buyer to correctly conclude that the claim is false?