Assignment 4 results

Assignment 4 results - a)Stratifiedrandomsampling...

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a) Stratified random sampling mean, st. dev and CI at 80% Stratum Vol. (x10^6gal) No of samples Epilimnion 5 8 8 6 11 Thermocline 1 2 11 16 Hypolimnion 14 10 25 27 18 Epilimnion Thermocline Hypolimnion Mean 10.5 13.5 16.2 Standard Error 1.64 2.5 2.05 Median 10 13.5 14 Mode #N/A #N/A 11 Standard Deviation 4.63 3.54 6.49 Sample Variance 21.43 12.5 42.18 Kurtosis -1.18 #DIV/0! -1.21 Skewness 0.14 #DIV/0! 0.66 Range 13 5 17 Minimum 4 11 10 Maximum 17 16 27 Sum 84 27 162 Count 8 2 10 Confidence Level(80.0%) 2.32 7.69 2.84 Weight of each stratum 5/20 1/20 14/20 0.25 0.05 0.7 Weighted average mean 14.64 Weighted average st dev. 1st calculate the weighted avg. variance 2.25 2nd take the square root of the weighted avg. variance 1.5 CI at 80% tw0-sided n 20 Student's t for one sided alpha =0.1 and df=19 1.33 (from t table) hence CI at 80% 14.19 15.09 b) Simple random sampling mean, st. dev and CI at 80% Vol. (x10^6gal) 20 x = w k × x k k = 1 r s 2 = w k 2 × s k 2 n k k = 1 r CI = x ± t n - 1 × s n
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No. of samples 20 N conc. (mg/L) 8 6 11 16 9 17 4 13 11 16 25 27 18 11 12 10 22 16 10 11
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This note was uploaded on 09/26/2011 for the course ES 462 taught by Professor Unc during the Spring '11 term at NMSU.

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Assignment 4 results - a)Stratifiedrandomsampling...

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