# The article cited in Exercise

The article cited in Exercise 21 also reported on another experiment in which the authors investigated whether the percent by weight of nickel in the alloy layer is affected by niobium powder paste thickness (A, at three levels), scanning speed (B, at three levels), and laser power (C, at three levels). One observation was made at each factor-level combination, yielding the accompanying data

a. Construct an ANOVA table for this experiment including only main effects and two-factor interactions (as did the authors of the cited article).

b. Use the appropriate F ratios to show that none of the two-factor interactions are significant at   .05.

c. Which main effects are significant at   .05?

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# The article cited in Exercise

The article cited in Exercise 78 of Chapter 7 gave additional data on breaking force (N):

a. Is there strong evidence for concluding that true average force in a dry medium at the higher temperature exceeds that at the lower temperature by more than 100 N?

b. Is there strong evidence for concluding that true average force in a wet medium at the lower temperature exceeds that at the higher temperature by more than 50 N?

Exercise 78

Acrylic bone cement is commonly used in total joint arthroplasty as a grout that allows for the smooth transfer of loads from a metal prosthesis to bone structure. The paper “Validation of the SmallPunch Test as a Technique for Characterizing the Mechanical Properties of Acrylic Bone Cement” (J. of Engr. In Med., 2006: 11–21) gave the following data on breaking force (N):

Assume that all population distributions are normal.

a. Estimate true average breaking force in a dry medium at 37° in a way that conveys information about reliability and precision. Interpret your estimate.

b. Estimate the difference between true average breaking force in a dry medium at 37° and true average force at the same temperature in a wet medium, and do so in a way that conveys information about precision and reliability. Then interpret your estimate.

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# The article cited in Exercise

The article cited in Exercise 25 of Section 8.2 gave the following data on mass crystallinity (in %) for 12 samples of the PHB polymer:

a. Is it plausible that the mass crystallinity for this type of polymer is normally distributed?

b. Suppose researchers wanted to investigate whether the true average mass crystallinity exceeds 40%. Carry out a test of appropriate hypotheses using a significance level of .05.

Exercise 25

Poly(3-hydroxybutyrate) (PHB), a semicrystalline polymer that is fully biodegradable and biocompatible, is obtained from renewable resources. From a sustainability perspective, PHB offers many attractive properties though it is more expensive to produce than standard plastics. The authors of “The Melting Behaviour of Poly(3-Hydroxybutyrate) by DSC. Reproducibility Study” (Polymer Testing, 2013: 215–220) wanted to investigate various physical properties of PHB by using a differential scanning calorimeter (DSC).

For each of 12 PHB specimens, the authors used a DSC to measure the melting point (in °C) of the polymer, which is the temperature for 99% completion of the fusion process.

A normal probability plot of the data shows a reasonably linear pattern, so it is plausible that the population distribution of PHB melting points as measured by DSC is at least approximately normal. The sample mean and standard deviation are 181.4 and .7242, respectively. Is there compelling evidence for concluding that true average melting point exceeds 181°C? Carry out a test of hypotheses using a significance level of .05.

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# The article cited in Exercise

The article cited in Exercise 31 of Section 8.2 gave the following observations on bending rigidity (­N ? m) for medium-quality fabric specimens, from which the accompanying Minitab output was obtained:

Would you use a one-sample t confidence interval to estimate true average bending rigidity? Explain your reasoning.

Exercise 31

Fusible interlinings are being used with increasing frequency to support outer fabrics and improve the shape and drape of various pieces of clothing. The article “Compatibility of Outer and Fusible Interlining Fabrics in Tailored Garments” (Textile Res. J., 1997: 137–142) gave the accompanying data on extensibility (%) at 100 gm/cm for both high-quality fabric (H) and poor-quality fabric (P) specimens:

a. Construct normal quantile plots to verify the plausibility of both samples having been selected from normal population distributions.

b. Construct a comparative boxplot. Does it suggest that there is a difference between true average extensibility for high-quality fabric specimens and that for poor-quality specimens?

c. The sample mean and standard deviation for the high-quality sample are 1.508 and .444, respectively, and those for the poor-quality sample are 1.588 and .530. Use the two-sample t test to decide whether true average extensibility differs for the two types of fabrics.

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# The article cited in Exercise

The article cited in Exercise 53 classified each member of the sample of workers with respect to both gender and level of work-related psychological demands. The following table is consistent with summary results reported in the article:

Does it appear that there might be an association between gender and work-related psychological demands? Carry out a test of hypotheses using the .05 significance level.

Exercise 53

We often think that occupational hazards are primarily experienced by those who work under dangerous conditions (e.g., construction workers, law enforcement officers, dockworkers). Clearly, a dangerous job can lead to illness or death. But can the psychological stress of a work environment affect employees’ overall health? This issue was investigated in the article “Are There Health Effects of Harassment in the Workplace? A Gender-Sensitive Study of the Relationships Between Work and Neck Pain” (Ergonomics, 2012: 147–159). The researchers wanted to identify workplace physical and psychosocial risk factors for neck pain among male and female workers. They also wanted to study the relationship between neck pain and intimidation or sexual harassment in the workplace. (Advanced statistical techniques were used to show that neck pain was significantly associated with intimidation at work among both male and female workers.)
This study was based on a representative sample (5405 men, 3987 women) of the Quebec working population. The following cross-classification table for this sample on gender versus level of neck pain is consistent with data reported in the article:

Does it appear that there might be an association between gender and neck pain? Carry out a test of hypotheses using the .01 significance level.

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# The article cited in Exercise

The article cited in Exercise 86 also included the following data on percentage of oil remaining for the commutator bearings:

Would you use the one-sample t confidence interval to estimate the population mean and median? Estimate the population median percentage of oil left using the interval suggested in Exercise 84, and determine the corresponding confidence level.

Exercise 84

The derailment of a freight train due to the catastrophic failure of a traction motor armature bearing provided the impetus for a study reported in the article “Locomotive Traction Motor Armature Bearing Life Study” (Lubrication Engr., Aug. 1997: 12–19). A sample of 17  high-mileage traction motors was selected and the amount of cone penetration (mm@10) was determined both for the pinion bearing and for the commutator armature bearing, resulting in the following data:

Calculate an estimate of the population mean difference between penetration for the commutator armature bearing and penetration for the pinion bearing, and do so in a way that conveys information about the reliability and precision of the estimate.

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