Assume that the helium porosity (in percentage) of coal samples taken from any p

Question

Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.74. a) Compute a 95% C places.) or the true average porosity o a certain seam the average porosity or 17 specimens om the sear was 48 aound your answer sto o decimal (D (b) Compute a 98% CI for true average porosity of another seam based on 12 specimens with a sample average porosity of 4.56. (Round your answers to two decimal places.) (C c) How large a sample size is necessary if the width of the 95% interval is to be 0.377(Round your answer up to the nearest whole number.) specimens (d) what sample size is necessary to estimate true average porosity to within 0.23 with 99% confidence? (Round your answer up to the nearest whole number) specimens

Explanation / Answer

a)

Standard error of the mean = SEM = S/N = 0.179

t(, N-1) = 2.12

Confidence interval = m +/- (t(, N-1)*SEM)

Mean = 4.85

Lower bound: 4.47

Upper bound: 5.23

b)

Standard error of the mean = SEM = S/N = 0.214

t(, N-1) = 2.491

Confidence interval = m +/- (t(, N-1)*SEM)

Mean = 4.56

Lower bound: 4.03

Upper bound: 5.09

c)

Sample Size = (Z* / Margin of Error)^2

= 95

Z(/2) = Z(95/2) = Z(47.5) = 1.96

(1.96*0.74/0.37)^2 = 16

d)

(2.58*0.74/0.23)^2 =69

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.