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webassian.net Assignment Suomission For this assignment, you submit answers by question parts. The number of submissions remaining for each question part only changes if you submit or change the answer. Assignment Scoring Your last submission is used for your score. 4/6 POINTS PREVIOUS ANSWERS DEVORESTAT9 7.5.005. MY NOTES ASK YOUR TEACHER Assume that the helium porosity (in percentage) of coal samples taken from any particular seam is normally distributed with true standard deviation 0.77. (a) Compute a 95% CI for the true average porosity of a certain seam if the average porosity for 24 specimens from the seam was 4.85. (Round your answers to two decimal places.) (4.53 5.17 (b) Compute a 98% CI for true average porosity of another seam based on 14 specimens with a sample average porosity of 4.56. (Round your answers to two decimal places.) ( 4.50 X , 5.10 X ) (c) How large a sample size is necessary if the width of the 95% interval is to be 0.42? (Round your answer up to the nearest whole number.) 52 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.) 75 specimens You may need to use the appropriate table in the Appendix of Tables to answer this question. Need Help? Read It Watch It Talk to Tutor Submit Answer