BIOL 4254 Stats Homework - CASEY NOYES

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Louisiana State University *

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4254

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Feb 20, 2024

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Name : Casey Noyes Section Number : 1 Each Research hypothesis relates to a data table. I.E. Research Hypothesis 1 is for Data Table 1. Through the assignment things in blue require an answer be supplied. Pattern: Bald eagle populations declined following the common use the pesticide DDT, but have recovered since it was banned in the United States and Canada. Write the overarching question that can be formed from the pattern above and would be answerable by results stemming from the reasonings below (1 pt): - How does the pesticide DDT affect bald eagle populations? _____________________________________________________________________ Research Hypothesis 1 (1 pt): The pesticide DDT decreases bald eagle populations by weakening their shells. Reasoning: DDT inhibits the calcification process of the eggshells making for weaker shells that break under the weight of the incubating adult, so there are fewer surviving young. Null Hypothesis 1 (1 pt): The pesticide DDT has no effect on the strength of bald eagle eggshells. Analytical Approach and Appropriate Graph type (1 pt): regression, scatterplot Independent Variable (1 pt): Presence/ absense of DDT Dependent Variable (1 pt): Number of bald eagles Research Hypothesis 2 (1 pt): Banning DDT increases bald eagle populations by strengthening their eggshells. Reasoning: The absence of DDT following the ban will lead to stronger shells and more surviving bald eagle young. Null Hypothesis 2 (1 pt): The absence of DDT following the ban will have no effect on the strength of bald eagle shells. Analytical Approach and Appropriate Graph type (1 pt): regression, scatterplot Independent Variable (1 pt): Presence/ absence of DDT Dependent Variable (1 pt): Number of bald eagles Research Hypothesis 3 (1 pt): Banning DDT reduces the amount of DDE present in eggs and increases eggshell viability. Reasoning: DDE is a product of DDT that can persist in eggs. The DDT ban will lead to a decline in DDE, which will lead to a healthier eggshell. Null Hypothesis 3 (1 pt): The absence of DDT following the ban will have no effect on the presence of DDE within bald eagle eggshells. Analytical Approach and Appropriate Graph type (1 pt): t-test, bar graph Independent Variable (1 pt): Presence/ absence of DDT Dependent Variable (1 pt): Presence/ absence of DDE 1

Research Hypothesis 4 (1 pt): Increased concentration of DDE decreases bald eagle productivity by reducing eggshell viability. Reasoning: Mean five year production is a measure of actual young hatched over a five year period (averaged to control for annual variation due to weather, etc.). If there were higher concentrations of DDE there would likely be thinner eggs and a reduction of actual production. Null Hypothesis 4 (1 pt): DDE levels within the eggshell will have no effect on bald eagle populations. Analytical Approach and Appropriate Graph type (1 pt): ANOVA, bar graph Independent Variable (1 pt): Concentration of DDE Dependent Variable (1 pt): Number of bald eagles. 2

Results Linear Regressions ● Insert the scatterplot that resulted from Table 1 below with all needed components (5 pts). Mean Number of Bald Eagles per Breeding Area (pre DDT ban) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Y = 211.7 - 0.1071*X R²: 0.674 1966 1967 1968 1969 1970 1971 1972 Year (pre DDT ban) Figure 1. The change in mean bald eagle population for the years leading up to the 1972 DDT ban. The data points represent the mean number of bald eagles per breeding area, with the shaded region representing the 95% confidence interval. ● Report the statistics from the statistical test of Table 1 with the appropriate format and interpret the results [Hint refer to the PowerPoint for the exact wording and values required] (2 pts). Analysis of table 1 indicates that there was a significant relationship between mean number of bald eagles per breeding area and the years leading up to the 1972 DDT ban (F 1,5 = 10.3211, p = 0.0237, y = 211.7 – 0.1071*X, Figure 1). Year progression accounted for 67% of the variation in bald eagle populations (R 2 = 0.6737). Therefore, there is statistical significance indicating that the progressive use of DDT prior to the DDT ban of 1972 was linked to the decrease of bald eagle populations. 3

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● Was the trend in the population between 1966 and 1972 positive or negative? Negative. The change in the population annually was -0.1071. [numeric value] (1 pt). ● Insert the scatterplot that resulted from Table 2 below (5 pts). Mean number of bald eagle young per breeding area (post DDT ban) 0.4 0.6 0.8 1.0 1.2 Y = -117.5 + 0.05988*X R²: 0.748 1972 1974 1976 1978 1980 Year (post DDT ban) Figure 2. The change in mean bald eagle population for the years immediately following the 1972 DDT ban. The data points represent the mean number of bald eagles per breeding area, with the shaded region representing the 95% confidence interval. ● Report the statistics from the statistical test of Table 2 with the appropriate format and interpret the results [Hint refer to the PowerPoint for the exact wording and values required] (2 pts). Analysis of table 2 indicates that there was a significant relationship in mean number of bald eagles per breeding area and the years immediately following the 1972 DDT ban (F 1,8 = 23.7690, p = 0.0012, y = -117.5 + 0.05988*X, Figure 2). Year progression accounted for 75% of the variation in bald eagle populations (R 2 = 0.748). Therefore, there is statistical significance indicating that the banning of DDT was related to the increase in the bald eagle population after 1972. 4

● Was the trend in the population between 1972 and 1981 positive or negative? Positive. The change in the population annually was 0.05988. [numeric value] (1 pt). T-test ● Insert bar graph of DDE concentrations pre and post DDT ban (Table 3) below with all needed components (5 pts). Figure 3. The parts per million (PPM) of DDE found within bald eagle eggshells following (post DDT ban) and prior to (pre DDT ban) 1972. Each bar represents the mean of DDE concentration in each 5-year period ( ± SE). ● Report the statistics from the statistical test of Table 3 with the appropriate format and interpret the results [Hint refer to the PowerPoint for the exact wording and values required] (2 pts). There was a significant difference in the mean of DDE concentrations between bald eagle eggshells measured pre DDT ban versus post DDT ban (t 6 = 5.0964, p = 0.0022, Figure 3). Average DDE concentration post DDT ban was 25.0 ± 10.753 (mean ± SE) and average DDE concentration pre DDT ban was 102.5 ± 10.753. 5

 Please specify what metric you used to make your determination of significance. (1 pt). I used an alpha ( 𝛼) value of 5% or 0.05. Therefore, because my p-value was less than my alpha (0.0022 < 0.05), I was able to reject the null hypothesis (H 0 ) and determine that there was a significant difference between the two trials. ANOVA ● Insert your bar graph of mean five year production and DDE intervals (Table 4) below with all needed components (5 pts). Figure 4. The mean five-year productivity for residual DDE intervals. Each bar represents the mean (± SE) of actual young hatched over a five-year period for various levels of DDE residues. Post hoc Tukey categories A and B are also indicated above each interval bar. ● Report the statistics from the statistical test of Table 4 with the appropriate format and interpret the results [Hint refer to the PowerPoint for the exact wording and values required] (2 pts). An analysis of variance (ANOVA) performed on table 4 indicated that there was a 6

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significant difference in the mean five-year production for varying residual DDE intervals (F 4,20 = 24.0917, p = <.0001, Figure 4). A post hoc Tukey test revealed that the mean value of five-year productivity was significantly different in groups with residual DDE levels above 3.6 (3.6-6.3, 6.3-12, and >12) and groups with levels below 3.6 (<2.2 and 2.2-3.6), noting that productivity significantly decreased once residual DDE levels were above 3.6. Although statistically insignificant, additional residual DDE past 3.6 continued to decline the productivity of bald eagle young with DDE levels above 12 showing the lowest productivity. ● Interpret the post hoc Tukey tests (2 pt). The post hoc Tukey test divided the levels of residual DDE into two statistically significant categories. Category A included the levels below 3.6 (<2.2 and 2.2-3.6) and category B included all levels above 3.6 (3.6-6.3, 6.3-12, and >12). This indicates that the difference in mean five-year production is statistically insignificant within the two levels of category A, but these levels are statistically different than those in category B (and vice versa). Interpretations and Connections – to be written in paragraphs using full sentences, not bullets. Paragraph 1  Specifically state whether the statistical results support or do not support your research hypothesis that bald eagle young declined in the years prior to the DDT ban (RH1). Please indicate what metric you used to determine if there is support for the research hypothesis (4 pts).  Specifically state whether the statistical results support or do not support your research hypothesis that bald eagle young increased in the years following the DDT ban (RH2). Please indicate what metric you used to determine if there is support for the research hypothesis (4 pts). ● Identify whether there is a significant relationship between the DDT ban and the mean number of bald eagle young per breeding area. Include whether the relationship is positive or negative (4 pts). ● Interpret what the prior two answers [Covering both before and after the ban, RH1 and RH2] means about the interaction between DDT and the populations of bald eagles overtime and the ecological effect on the bald eagle populations. Include what would happen to the populations if nothing had been done about DDT use and the logical connection between DDT and the bald eagle populations [Hint: look at your reasonings] (4 pts). My first research hypothesis (RH1) suggested that bald eagle populations decreased due to the use of pesticide DDT. This hypothesis is supported by Figure 1 and its associated tests, which show a significant negative relationship between DDT presence and mean bald eagle population per breeding area. This significance is confirmed by the t-test p-value (p = 0.0237) which is less than our designated alpha ( 𝛼 = 0.05), allowing us to reject our null hypothesis (H 0 ). Inversely, the second 7

hypothesis (RH2) suggested that bald eagle populations would increase again in the absence of DDT. Thus, using data following the DDT ban of 1972, we were able to confirm the positive relationship (y = -117.5 + 0.05988*X) between the mean bald eagle population and the years since DDT banning (Figure 2). Once again, our p- value (p = 0.0012) for this research was below our designated 𝛼 , allowing us to reject H 0 . Combining both of these research trials allows us to determine that there is a significant positive relationship between the DDT ban and bald eagle populations, meaning that the populations increased upon activation of the ban. We are then able to conclude that the pesticide DDT does negatively impact bald eagle populations by inhibiting the calcification of bald eagle eggshells, rendering the weakened shells susceptible to damage by incubation and other natural factors. If the DDT pesticide ban was not enacted in 1972, this impact would have severely reduced bald eagle populations and possibly caused extinction of the species. Paragraph 2 ● Specifically state whether the statistical results support or do not support your research hypothesis that the DDT ban would reduce DDE residues in bald eagle eggs (RH3). Please indicate what metric you used to determine if there is support for the research hypothesis (4 pts). ● Explain why DDE residues might be lower after the DDT ban and what this result combined with the prior information, means about the relationship between DDT, DDE, and eagle eggs, as well as what ecological effect results from these interactions in terms of the retention time of environmental contaminants and how these secondary chemicals can be of concern (4 pts). Analyzing DDE residues present in the years following the DDT ban allowed us to conclude that there is a significant relationship between use of the pesticide DDT and DDE levels in bald eagle eggshells. This relationship is indicated in Figure 2 and is supported by the p-value (0.0022) being less than our designated 𝛼. Additionally, the decrease of DDE residues following the ban of DDT allows us to conclude that DDE is a product of, and is positively related to, DDT. We are then able to infer that the presence of DDE within an eggshell will indicate inhibited calcification and decreased bald eagle population similarly to its parental chemical, DDT. This also shows that, although DDT was no longer used in the breeding areas of bald eagles, the secondary chemical was still present in the eagle eggshells several years after its banning, thus indicating that environmental contaminants can have negative effects that persist far longer than the chemical itself is present for. Paragraph 3 ● Specifically state whether the statistical results support or do not support your research hypothesis that the mean five year production would increase with a decrease in DDE residue. Please indicate what metric you used to determine if there is support for the research hypothesis (4 pts). ● Finally, take all of the information you have used in this section and synthesize 8

a final summary of the effects of DDT on the bald eagle populations. You must include the information from paragraph 1 [RH1, RH2] and paragraph 2 [RH3] and add in the new information for RH4. Explain the impacts of both the introduction and ban of DDT on the bald eagle populations and what the different concentrations of DDE and 5 year productivity tell us about the populations of eagles in both time periods [pre- or post-ban]. Use these connections to predict the final outcome of eagle populations without a ban and potential issues that the eagles could still face. These predictions should be the overall ecological effects and long term ecological impacts (18 pts). Our final research hypothesis (RH 4 ) suggested that the decrease of DDE residues within bald eagle eggshells would improve their mean productivity. Figure 4 supports this research with the ANOVA p-value (p = <.0001) being less than our designated 𝛼 . The post hoc Tukey test gave us additional information, noting that there is a significant increase in bald eagle productivity once DDE levels drop below 3.6. Overall, by examining DDT and DDE data in the years prior and following the DDT ban, we were able to determine that DDT does have a significant negative impact on bald eagle populations. First, RH1 and Figure 1 showed us how the mean bald eagle population decreased in the years prior to the DDT ban, indicating that DDT was negatively impacting the birds’ overall fitness. Then, RH2 and Figure 2 confirmed this effect by showcasing how the mean bald eagle population increased again in the years immediately following the DDT ban. We then looked at the secondary chemical of the pesticide DDT, DDE. RH3 and Figure 3 allowed us to visualize the significant difference in residual DDE found in eggshells when DDT was in use versus when it was banned. This visualization confirmed that DDE is a product of, and directly related to, DDT. Lastly, RH4 and Figure 4 represents the significant increase in fitness that young bald eagles have when DDE residues are decreased. The completed bar graph, including standard deviation and Tukey test categories, allowed us to recognize that bald eagle eggshells with DDE levels below 3.6 are significantly more suited to survive than their higher-DDE concentrated counterparts. Therefore, we can conclude that, if DDE levels continue to decrease, the mean population values of bald eagles should increase back to what they were before the introduction of pesticide DDT. However, if residual DDE remains in bald eagle populations despite the ban, their overall fitness will remain negatively impacted by the long-term effects of environmental contamination. Inversely, if pesticide DDT was never subjected to the 1972 ban, DDE levels would have continued to rise and likely lead to continued worsening eggshell viability and complete extinction of the bald eagle populations. 9

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BIOL 4254 Stats Homework - CASEY NOYES

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