A Design Engineer Wants to Construct a Sample Mean Chart

question 75

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: $$\begin{array} { c c c c c } \text { Sample } && { \text { Service Life (hours) } } \\\hline 1 & 495 & 500 & 505 & 500 \\2 & 525 & 515 & 505 & 515 \\3 & 470 & 480 & 460 & 470\end{array}$$
What is the standard deviation of the sampling distribution of sample means for whenever service life is in control?

• A) 5 hours
• B) 6.67 hours
• C) 10 hours
• D) 11.55 hours
• E) 20 hours

---

Definitions:

Marginal Tax Rate

The tax rate that applies to each additional dollar of income, indicating how much of the next dollar earned will be taken in taxes.

Average Tax Rate

Average Tax Rate is the proportion of the total income paid as taxes, calculated by dividing the total taxes by the total taxable income.

Total Taxes

The combined amount of all the taxes imposed by a government on an individual or business, including income tax, property tax, sales tax, etc.

Average Tax Rate

The proportion of total income that is paid in taxes, calculated by dividing the total tax paid by the total income.