Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.78.(c) How large a sample size is necessary if the width of the 95% interval is to be 0.31? (Round your answer up to the nearest whole number.)? specimens(I have answers for a, b, and d I just need help with c, the answer is not 24.32) Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.78.(a) Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 21 specimens from the seam was 4.85. (Round your answers to two decimal places.)4.525.18(b) Compute a 98% CI for true average porosity of another seam based on 11 specimens with a sample average porosity of 4.56. (Round your answers to two decimal places.)( 4.015.11(c) How large a sample size is necessary if the width of the 95% interval is to be 0.31? (Round your answer up to the nearest whole number.)25X specimens(d) What sample size is necessary to estimate true average porosity to within 0.21 with 99% confidence? (Round your answer up to the nearest whole number.)92specimensYou may need to use the appropriate table in the Appendix of Tables to answer this question.

Answered: ssume that the helium porosity (in…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.78.

(c) How large a sample size is necessary if the width of the 95% interval is to be 0.31? (Round your answer up to the nearest whole number.)

? specimens

(I have answers for a, b, and d I just need help with c, the answer is not 24.32)

Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.78.
(a) Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 21 specimens from the seam was 4.85. (Round your answers to two decimal places.)
4.52
5.18
(b) Compute a 98% CI for true average porosity of another seam based on 11 specimens with a sample average porosity of 4.56. (Round your answers to two decimal places.)
( 4.01
5.11
(c) How large a sample size is necessary if the width of the 95% interval is to be 0.31? (Round your answer up to the nearest whole number.)
25
X specimens
(d) What sample size is necessary to estimate true average porosity to within 0.21 with 99% confidence? (Round your answer up to the nearest whole number.)
92
specimens
You may need to use the appropriate table in the Appendix of Tables to answer this question.

Features Features Normal distribution is characterized by two parameters, mean (µ) and standard deviation (σ). When graphed, the mean represents the center of the bell curve and the graph is perfectly symmetric about the center. The mean, median, and mode are all equal for a normal distribution. The standard deviation measures the data's spread from the center. The higher the standard deviation, the more the data is spread out and the flatter the bell curve looks. Variance is another commonly used measure of the spread of the distribution and is equal to the square of the standard deviation.

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