Question

Identical soil samples were sent to 2 testing labs to determine the levels of polychlorinated biphenyl (PCB) contamination. Results reported for 8 replicates by Lab A 249 (+-13) ppb and Lab B 283 (+- 35) ppb respectively.

a) If the soil sample is certified to contain 267 ppb of PCB, does any of the labs appear to have a systematic error?

Answer 1

Identical soli sample sent to 2 testing labs to determine the levels of polychlorinated biphenyl (PCB) contamination.

Lab A result:  Contain of PCB is 249 (with error of +-13) ppb, hence range of result is from 236 to 262 ppb.

Lab B result:  Contain of PCB​​​​​​​ is 283 (with error of +-35) ppb, hence range of result is from 248 to 318 ppb.

Actual contain of PCB​​​​​​​ is 267 ppb.

Hence Actual contain of PCB​​​​​​​ (276 ppb) is within the range of Lab B result (248 to 318 ppb).

Hence Lab B appear to have a systematic error.