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

---

Definitions:

Young Children

Refers to individuals in the early stages of life, typically considered to be between infancy and the early school years.

Older Children

Refers to children typically in the later stages of childhood, approaching adolescence, often characterized by more advanced cognitive and social development compared to younger children.

Common

Referring to something that occurs frequently or is widely accepted or shared.

Right- and Left-Handedness

The preference most people show for using one hand over the other, often evident in tasks such as writing.