An experiment was conducted to investigate the rodding of concrete to remove ent

Question

An experiment was conducted to investigate the rodding of concrete to remove entrapped air. A 3 inch by 6 inch cylinder was used and the number of times the rod was used was changed in the experiment. The response was the resulting compressive strength of the concrete specimen. The data are in the following table.

3b) Based on the following computer output evaluate whether mean etch rates are the same for the different RF power values.

Choose the best answer from the following:

i) The mean etch rates are all not the same. The sample means for the etch rates 10 and 25 are the same (they are both 1500); however the sample mean for etch rate 15 equals 1586.7 and the sample mean for etch rate 20 equals 1606.7. One-way ANOVA: Strength versus Rodding Level DF Source Rodding Level 3 28633 9544 1.87 0.214 Error Total MS 8 40933 5117 11 69567 S- 71.53 R-Sq 41.16% R-Sq (adj) -19.09% - Individual 95% CIs For Mean Based on Pooled StDev Level N 10 15 20 25 Mean StDeV ----+---+---+---+--- 3 1500.0 52.0( 3 1586.777.7 3 1606.7 107.9 3 1500.0 10.0( 1440 1520 1600 1680 Pooled StDev = 71.5

Explanation / Answer

option (iii) and (iv) are correct (if need only one choose iii)

iii) The means for the different etch rates could all be the same because the 95% confidence intervals all overlap

iv) The means for the different etch rates could all be the same because the p-value for testing the null hypothesis that the means are all equal is greater than .05

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