Chapter 6 – Instructor Reserve Problems
These are additional problems that instructors might use. Data may be found on
worksheets in the Excel workbook Ch 06 Instructor Reserve Problem Data.
1. Receiving inspection technicians at SelCells, Inc., a cellphone retailer took a sample of
250 incoming phones, as shown in the table found in the worksheet Prob 06-01.
a. Find the proportion of defective phones in the sample that are classified as defective
(having at least one feature that did not operate properly) by using the Excel COUNTIF
2. Plastic panels are made by Panlmastr Company. The average number of defects per panel
is 0.8. If these data follow a Poisson distribution, use the Poisson spreadsheet template to
answer the following questions.
a) What is the probability of finding exactly 4 defects in a plastic panel chosen at
random?
3. The production manager at Evansrode Marine Engines is investigating a new process
which makes a 36 inch shaft used in outboard motors. Since this is a new process, she
wants to get descriptive statistics that can be used in later studies to determine the
4. A manufacturer of a printer determines that the mean number of days before a cartridge
runs out of ink is 75 days, with a standard deviation of 6 days. Assuming a normal
distribution, what is the probability that the number of days will be less than 67.5 days?
More than 88?
5. Tio Anciano tequila is sold in 1 liter (1000 milliliter) bottles. The standard deviation for
the filling process is 10 milliliters. If the process requires a 2 percent, or smaller,
probability of over-filling, defined as over 990 milliliters, what must the target mean for
the process be?
6. The mean filling weight of salt containers processed by the Piedra Salt Co. is 15.5
ounces. If 1 percent of the containers contain more than 16 ounces, what is the standard
deviation of the filling weight of the containers?
7. Cheez-D-Lite snack cracker boxes have been found to have a standard deviation of 10
grams and a mean of 412 grams. How many grams should be specified to ensure that 95
percent of the boxes will contain more than this weight?
8. SelCells, Inc., the cellphone retailer mentioned in problem 1, above, uses a large number
of common batteries in one of its most popular lines of phones. After testing a large
number of them, they found that the average time to failure is 1/
= 7800 hours.
a) What is the probability that a component will fail within 1000 hours? After 7800
hours?
10. Qualiparts, a supplier of parts to the auto industry, wants to test to determine if the
strength of wire used to make alternators is significantly higher for any of four potential
subcontractors. The four subcontractors agreed to submit sample information from 10
samples, using a standardized test provided by Qualiparts, as provided in the worksheet
Prob 06-10. Use the single factor ANOVA Excel tool to determine if there is a significant
difference between the strength scores of the four contractors at the 5 percent level.
11. Durrarub, Inc. makes rubber doors sealing accessories for industrial uses. The company
wants to test how closely the hardness of their door sealing products is correlated with
temperature. It is known that the higher the temperature, the lower the hardness,
12. RocketSci uses two main ingredients to make rocket fuel used to power rocket engines
for space missions. They are ammonium perchlorate powder (the oxidizer), and fine
aluminum powder (the fuel), held together by a binder of petroleum based rubber with