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INTRODUCTION Location of study: Embercombe/ Nutscale Waters Exmoor National Park Date of study: 21st June 2003 PREDICTIONS 1. Hypothesis: There is a greater abundance of blackfly larvae (Simuliidae) in riffles than in pools. 1. (Ho): There is no difference between the abundance of blackfly larvae (Simuliidae) in riffles and pools. 2. Hypothesis: There will be a positive relationship between the abundance of blackfly larvae (Simuliidae) and the velocity (cm.s-1) of the water. 2. (Ho): There is no relationship in the abundance of blackfly larvae (Simuliidae) in water with high or low velocity of the water. 3. Hypothesis: There will be a negative relationship between the abundance of water beetles and flatworms and the abundance of blackfly larvae (Simuliidae). 3. (Ho): There is no relationship between the abundance of water beetles, flatworms and blackfly larvae (Simuliidae). CLASS RESULTS TABLE  Abiotic factors Averages  RESULTS (from the above table that applies to my coursework)  ANALYSING DATA The Chi test for the significance of the difference in the abundance of blackfly larvae (Simuliidae) Categories of results Chi ( ) = (O - E) . E = 24.1 + 24.1 = 48.2 Degrees of freedom = no. of categories - 1 = 1 5% significance, critical value of 3.84 Chi is greater than the critical value, therefore I am 95% confident there is a significant difference in the abundance of blackly larvae (Simuliidae) in pools and riffles so I can reject my Ho at a 5% significance level and 95% confidence limits. 1% significance, critical value of 6.64 Chi is also greater than the critical value, so I am 99% confident there is a significant difference in the abundance of blackly larvae (Simuliidae) in pools and riffles so I can reject my Ho at the 1% significance level and 99% confidence limits. Spearman’s Rank Correlation Co-efficient to test for the strength of a positive correlation between velocity (cm.s-1) and the abundance of blackfly larvae (Simuliidae) Number of pairs (n) Velocity (cm.s-1) Rank Blackfly larvae Rank Difference Difference (D ) 1 4.2 10 3 9 1 1 2 17.6 5 20 2 3 9 3 5.6 7 7 5.5 2.5 6.25 4 27.3 1 13 4 -3 9 5 4.3 8.5 5 7.5 1 1 6 19.3 2 5 7.5 -5.5 30.25 7 4.3 8.5 1 10 -1.5 2.25 8 18.8 3 43 1 2 4 9 9.0 6 7 5.5 0.5 0.25 10 18.0 4 19 3 1 1 D = 64 Rs: 1 - (6 D ) .n - n 1 - 384 990 Rs = 0.612 Significance level = 5% Number of pairs of values = 10 Critical value (CV) from table = 0.648 The value of Rs is less than the CV, therefore I accept my Ho at the 5% significance level and 95% confidence limits. Spearman’s Rank Correlation Co-efficient to test for the strength of a negative correlation between the abundance of water beetles and the abundance of blackfly larvae (Simuliidae) Number of pairs (n) Water beetles Rank Blackfly larvae Rank Difference Difference (D ) 1 3 4 3 9 -5 25 2 0 10 20 2 8 64 3 1 7.7 7 5.5 2 4 4 1 7.5 13 4 3.5 12.25 5 6 2 5 7.5 -5.5 30.25 6 3 4 5 7.5 -3.5 12.25 7 16 1 1 10 -9 81 8 1 7.5 43 1 6.5 42.25 9 3 4 7 5.5 -1.5 2.25 10 1 7.5 19 3 4.5 20.25 D = 293.50 Rs = 1 - (6 D ) .n - n 1 - 1761 990 = -0.7788 Significance level = 5% Number of pairs of values = 10 Critical value (CV) from table = -0.648 The value of Rs is greater than the CV therefore I am 95% confident that there is a negative correlation between the abundance of water beetles and blackfly larvae, so I can reject my Ho at the 5% significance level and 95% confidence limits. Spearman’s Rank Correlation Co-efficient to test for the strength of a negative correlation between the abundance of flatworms and the abundance of blackfly larvae (Simuliidae) Number of pairs (n) Flatworms Rank Blackfly larvae Rank Difference Difference (D ) 1 0 9.5 3 9 0.5 0.25 2 0 9.5 20 2 7.5 56.25 3 34 1 7 5.5 -4.5 20.25 4 25 2 13 4 2 4 5 4 4 5 7.5 -3.5 12.25 6 3 6 5 7.5 -1.5 2.25 7 2 8 1 10 -2 4 8 3 6 43 1 5 25 9 5 3 7 5.5 -2.5 6.25 10 3 6 19 3 3 9 D = 139.5 Rs = 1 - (6 D ) .n - n = 1 - 837 990 = 0.1545 Significance level = 5% Number of pairs of values = 10 Critical value (CV) from table = 0.648 The value of Rs is less than the CV, therefore I accept Ho at the 5% significance level and 95% confidence limits.
Approximate Word count = 2645
Approximate Pages = 10.6
(250 words per page double spaced)
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