3. + -/10 points DevoreStat99.?.503XP My Notes Ask Your The accompanying table g

Question

3. + -/10 points DevoreStat99.?.503XP My Notes Ask Your The accompanying table gives summary data on cube compressive strength (N/mm2) for concrete specimens made with a pulverized fuel-ash mix. Sample Sample Size 67 72 Sample Age (days) Mean 25.97 34.78 SD 4,87 6.48 28 Calculate a 99% CI for the difference between true average 7-day strength and true average 28-day strength. (Use Ho: H7 -H280. Round your answers to two decimal places.) N/mm2 Interpret your 99% CI. 0 with 99% confidence, that the true difference falls outside these values 0 with 99% confidence, that the true difference falls below the lower bound. with 99% confidence, that the true difference falls above the upper bound O with 99% confidence, we can say that the true difference falls between these values

Explanation / Answer

The statistical software output for this problem is:

Two sample T summary confidence interval:
?1 : Mean of Population 1
?2 : Mean of Population 2
?1 - ?2 : Difference between two means
(with pooled variances)

99% confidence interval results:

Hence,

99% confidence interval:

(-11.36, -6.26) N/mm2

Interpretation: Option D is correct.

Difference Sample Diff. Std. Err. DF L. Limit U. Limit ?1 - ?2 -8.81 0.97788651 137 -11.364427 -6.2555727

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