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Effect of Mouthwash on E-Coli Bacteria

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Introduction

Interpreting and Evaluating Mann-Whitney U test I have decided that I would like to use the Mann-Whitney U test to interpret and evaluate my data. This is because I would like to compare data sets to see whether the medians from the different brands of mouthwash I investigated were significantly different from one another as I have unmatched data and this would help me to demonstrate their differences clearly. Effect of Mouthwash on E-Coli Bacteria Results For E-Coli Result No. Mouthwash A (mm) Mouthwash B (mm) Mouthwash C (mm) Mouthwash D (mm) 1 2.14 4.65 6.22 1.81 2 1.88 3.86 5.34 1.98 3 2.46 4.39 4.82 2.12 4 2.79 4.29 6.10 1.88 5 2.74 3.35 4.98 2.06 6 2.54 3.23 5.40 1.91 7 2.81 4.12 5.83 2.43 8 1.95 3.54 5.17 1.78 9 2.65 4.16 5.51 1.65 10 2.27 3.48 5.65 1.54 Average 2.423 3.907 5.502 1.916 Average Results Mouthwash A B C D Median (mm) 2.423 3.907 5.502 1.916 Ranking the Data 1) Mouthwash C 2) Mouthwash B 3) Mouthwash A 4) Mouthwash D ? R1 (Mouthwash C) = 55.02 ? R2 (Mouthwash B) = 39.07 ? R3 (Mouthwash A) = 24.23 ? R4 (Mouthwash D) = 19.16 Comparison of Mouthwash A against B: U1 = ( n x n ) + (0.5n ) (n + 1) ...read more.

Middle

- 39.07 = 115.93 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 19.16 = 135.84 Smaller Value = 115.93 Critical Value for U = 23 115.93 > 23 Comparison of Mouthwash C against D: U1 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 55.02 = 99.98 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 19.16 = 135.84 Smaller Value = 99.98 Critical Value for U = 23 99.98 > 23 Effect of Mouthwash on Microccus Liteus Bacteria Result No. Mouthwash A (mm) Mouthwash B (mm) Mouthwash C (mm) Mouthwash D (mm) 1 7.30 5.04 7.86 4.21 2 7.81 6.49 7.73 4.50 3 8.45 6.98 7.62 3.38 4 8.72 5.79 7.36 3.47 5 8.64 6.24 6.89 4.95 6 7.94 5.72 6.56 4.13 7 8.58 5.37 7.34 3.91 8 8.63 5.21 6.71 3.86 9 8.36 6.13 7.25 3.22 10 7.79 5.67 7.17 3.34 Average 8.222 5.864 7.252 3.897 Order of Zone of Clearance of Microbial Decay (Highest to Lowest) ...read more.

Conclusion

+ (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 39.07 = 115.93 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 55.02 = 99.98 Smaller Value = 99.98 Critical Value for U = 23 99.98 > 23 Comparison of Mouthwash B against D: U1 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 39.07 = 115.93 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 19.16 = 135.84 Smaller Value = 115.93 Critical Value for U = 23 115.93 > 23 Comparison of Mouthwash C against D: U1 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 55.02 = 99.98 U2 = ( n x n ) + (0.5n ) (n + 1) - ? R U1 = (10 x 10) + (0.5[10]) (10 + 1) - 19.16 = 135.84 Smaller Value = 99.98 Critical Value for U = 23 99.98 > 23 From the data collected from my statistical test I can see that ...read more.

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Statistical test only** A worked example of the Mann-Whitney U test that has been calculated well but has not been interpreted at all by the candidate.
The statistic has been used correctly and calculated using the formulae for large sample size. A faster method is available for the small sample size used.
To improve- The real point of carrying out statistical tests is to see if there is true significance in the data collected and then interpret and evaluate the experiment accordingly. This candidate has unfortunately not discussed the meaning of the statistic at all.
If the U value is equal to or less than that in the U value table the null hypothesis can be rejected. The difference in these samples is significant at the 2% level.

Marked by teacher Stevie Fleming 26/07/2013

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