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: $$\begin{array} { c c c c c }
\text { Sample } & { \text { Service Life (hours) } } \
\hline 1 & 495 & 500 & 505 & 500 \
2 & 525 & 515 & 505 & 515 \
3 & 470 & 480 & 460 & 470
\end{array}$$
What is the sample mean service life for sample 2?
A) 460 hours
B) 495 hours
C) 500 hours
D) 515 hours
E) 525 hours

Question

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: $$\begin{array} { c c c c c } 
\text { Sample } & { \text { Service Life (hours) } } \
\hline 1 & 495 & 500 & 505 & 500 \
2 & 525 & 515 & 505 & 515 \
3 & 470 & 480 & 460 & 470
\end{array}$$
What is the sample mean service life for sample 2?
A) 460 hours
B) 495 hours
C) 500 hours
D) 515 hours
E) 525 hours

Quizplus · Accepted Answer

In order to find the sample mean service life for sample 2, we need to calculate the mean of the sample.

Sample 2: (525 + 515 + 505 + 515)/4 = 515

Therefore, the sample mean service life for sample 2 is 515 hours.

The best choice is D.

A Design Engineer Wants to Construct a Sample Mean Chart