The Journal of Testing and Evaluation (July 1992) published an investigation of the mean compression strength of corrugated fiberboard shipping containers.
Comparisons were made for boxes of five different sizes: A, B, C, D, and E.Twenty identical boxes of each size were independently selected and tested, and the peak compression strength (pounds) recorded for each box. Thc figure below shows the sample means for the five box types as well as the variation around each sample mean.

a. Explain why the data is collected as an independent samples design.

b. Refer to box types B and D. Based on the graph, does it appear that the mean compressive strengths of thesc two box types are significantly different?
Explain.

c. Based on the graph, does it appear that the mean compressive strengths of all five box types are significantly different? Explain.
A B C D E Box type Source: Singh, S. F! , et al. "Compression of single-wall corrugated shipping containers using fixed and floating test platens." Journal of Testing and Evaluation, Vol. 20, No. 4, July 1092, p. 319 (Figure 3). Copyright American Society for Testing and Materials. Reprinted with permission.