Question

An article in the ACI Materials Journal (Vol. 84, 1987, pp. 213-216) describes several experiments investigating the rodding of concrete to remove trapped air. A 3-inch × 6-inch cylinder was used, and the number of times this rod was used is the design variable. The resulting compressive strength of the concrete specimen is the response. The data are shown in the following table.

13.2.7 An article in the ACI Materials Journal (Vol. 84, 1987, pp. 213-216) describes several experiments investigating the rodding of concrete to remove trapped air. A 3-inch x 6-inch cylinder was used, and the number of times this rod was used is the design variable. The resulting compressive strength of the concrete specimen is the response. The data are shown in the following table. Compressive Strength (psi) Rodding Level Observations 10 1530 1530 1440 15 1610 1650 1500 20 1560 1730 1530 25 1500 1490 1510 (a) Is there any difference in compressive strength due to the rodding level? Use a 0.05. Calculate to 2 decimal places fo! Is there statistical evidence to say that rodding level affects compressive strength? (b) Find to 2 decimal places the P-value for the Fstatistic computed in part (a). P-value = (c) Analyze the following residual plots to determine model adequacy. Does the assumption of normality seem reasonable? Does there appear to be an outlier in the data? Does the assumption of constant variance seem reasonable?

Answer 1

. Answer By the given data, a: To test the bypothesis is that there is a difference in compressive strength due to the rodding level at 5.7 level of signific ficate Hejpothesis are, Ho il = M = M = lly Ha: at least one is unequal. orie ili ANOVA Source SS de MS F P-value Groups Between 28633.33 3 9544.44 1865. 10:214 Groups Within 140933.3318 511 6.64 69566-66 11 Total Evalue 1.865 1.87 CS Scanned with CamScanner

Decision The . so conclugion is that po value Y c'05. ve failed to rejeet H. There is insufficient Evidenice to indicate that there a difference in compre ssive strength due to rodding level. The result is not statistically significant Ans: No bol 01214 0-21 value .co oyes (i) No (ii) Yes CS Scanned with CamScanner