The accompanying table gives summary data on cube compressive strength (N/mm2) for concrete specimens made with a pulverized fuel-ash mix.Age(days) Sample Size Sample Mean Sample SD7 6926.944.8428 7135.776.46Calculate a 99% CI for the difference between true average 7-day strength and true average 28-day strength. (Use H0: ?7 − ?28 = 0. Round your answers to two decimal places.) , N/mm2 Determine the number of degrees of freedom for the two-sample t test or CI in each of the following situations. (Round your answers down to the nearest whole number.)(a) m = 12, n = 10, s1 = 5.0, s2 = 6.0 (b) m = 12, n = 15, s1 = 5.0, s2 = 6.0 (c) m = 12, n = 15, s1 = 4.0, s2 = 6.0 (d) m = 10, n = 24, s1 = 5.0, s2 = 6.0

Answered: The accompanying table gives summary…

Holt Mcdougal Larson Pre-algebra: Student Edition 2012

1st Edition

ISBN:9780547587776

Author:HOLT MCDOUGAL

Publisher:HOLT MCDOUGAL

Chapter1: Variables, Expressions, And Integers

Section1.5: Adding Integers

Problem 45E

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Question

The accompanying table gives summary data on cube compressive strength (N/mm²) for concrete specimens made with a pulverized fuel-ash mix.

Age (days)	Sample Size	Sample Mean	Sample SD
7	69	26.94	4.84
28	71	35.77	6.46

Calculate a 99% CI for the difference between true average 7-day strength and true average 28-day strength. (Use H₀: ?₇ − ?₂₈ = 0. Round your answers to two decimal places.)

N/mm²

^{Determine the number of degrees of freedom for the two-sample t test or CI in each of the following situations. (Round your answers down to the nearest whole number.)}

(a)    m = 12, n = 10, s₁ = 5.0, s₂ = 6.0

(b)    m = 12, n = 15, s₁ = 5.0, s₂ = 6.0

(c)    m = 12, n = 15, s₁ = 4.0, s₂ = 6.0

(d)    m = 10, n = 24, s₁ = 5.0, s₂ = 6.0

Expert Solution

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Hi! Thank you for the question. As per the honor code, we are allowed to answer 1 question at a time, so we are answering the first question as you have not mentioned which of these you are looking for. Please re-submit the question separately for the remaining questions.

Let $μ_{7} and σ_{7}$ denote respective the population mean and standard deviation for 7-day strength.

Let $μ_{28} and σ_{28}$ denote respective the population mean and standard deviation for 28-day strength.

Given that $n_{7} = 69, {\bar{x}}_{7} = 26.94, s_{7} = 4.84, n_{28} = 71, {\bar{x}}_{28} = 35.77, s_{28} = 6.46, confidence level = 0.99$ .