3. X-rays and lasers are sometimes used to inspect solder-joint defects on print

Question

3. X-rays and lasers are sometimes 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 on average at least 10 solder joints per second. The equipment was tested by a potential buyer on 48 different PCBs and the results are recorded in the spreadsheet "PCB" posted on Canvas (a) The potential buyer wants to know whether the sample data refutes the manufac- turer's claim. Specify the null and alternative hypotheses that the buyer should test (b) Conduct the hypothesis test described in part (a) an interpret the results of the H test

Explanation / Answer

a)

H0<10

H1=>10

b)

tSTAT=X-µ/S/n

  =9.29-10/2.10/48

=0.71/2.10/6.93

=2.34

n=48, so df=47 and here we have one tailed test. tCRIT=1.6799. tSTAT is greater than tCRIT. Hence reject the null hypothesis. Hence, manufacturer’s claim is valid about inspecting atleast 10 solder joints per second.

Values 10 12 7 9 9 9 11 12 9 8 10 10 9 10 12 9 10 8 11 11 9 10 10 7 10 9 9 10 7 8 0 9 11 6 9 12 12 7 10 9 9 10 13 8 6 9 11 10 9.291667 Average 2.103273 Std Dev

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