A Design Engineer Wants to Construct a Sample Mean Chart

question 59

Multiple Choice

A design engineer wants to construct a sample mean chart for controlling the service life of a halogen headlamp his company produces. He knows from numerous previous samples that this service life is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent production batches, he tested service life on random samples of four headlamps, with these results: $$\begin{array} { c c c c c } \text { Sample } && { \text { Service Life (hours) } } \\\hline 1 & 495 & 500 & 505 & 500 \\2 & 525 & 515 & 505 & 515 \\3 & 470 & 480 & 460 & 470\end{array}$$
If he uses upper and lower control limits of 520 and 480 hours, on what sample(s) (if any) does service life appear to be out of control?

• A) sample 1
• B) sample 2
• C) sample 3
• D) both samples 2 and 3
• E) all samples are in control

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Definitions:

Primary

Referring to the first or most significant stage, condition, or rank.

Secondary

Pertaining to the second level or stage in a sequence or process, often implying a subordinate or lesser importance than the primary.

Tertiary

Referring to the third level or stage of something, often used in education (tertiary education) or in structures and processes.

Psychotropic Medication

Any medication capable of affecting the mind, emotions, and behavior, typically used in the treatment of mental health disorders.