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 (H) fabric and poor-quality (P) fabric specimens. H 1.2 .9 .7 1.0 1.7 1.7 1.1 .9 1.7 1.9 1.3 2.1 1.6 1.8 1.4 1.3 1.9 1.6 .8 2.0 1.7 1.6 2.3 2.0
P 1.6 1.5 1.1 2.1 1.5 1.3 1.0 2.6
a) Construct normal probability plots to verify the plausibility of both samples having been selected from normal population distributions.
b) Construct a comparitive 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 SD for the HQ are 1.508 and .444 respectively and those for the PQ are 1.588 and .530. Use the two sample t test to decide whether the true average extensibilty differs for the two types of fabrics.