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Sampling and Statistics Fisheries Management 4300 Problem Set #1 Fall 2012 1) Provided in the Excel spreadsheet are length data for walleyes sampled from Glen Elder Reservoir (GLER) and Marion Reservoir (MARR). A) Estimate: Estimate Mean Median Mode Variance Standard deviation Standard error Coefficient of variation (use SD) GLER MARR B) What do the values indicate about each population? Does one population tend to have larger fish than the other population? Is there more variation in one population compared to the other? C) If you wanted to test whether the mean length of walleyes differed between populations, which statistical test might you use and why? Can you do it in Excel? If so, do it and report your results 2) Provided in the Excel spreadsheet are fish (bluehead sucker) and habitat data collected from several reaches of a desert stream in Wyoming. A) Fit a linear regression to (1) the number of fish (dependent) versus width (independent) and (2) number of fish (dependent) versus the proportion of silt substrate (independent). For each regression provide the regression equation, identify the slope and intercept values, correlation coefficient (r), and coefficient of determination (r2). Equation βo β1 r r2 Fish vs. width Fish vs. silt Interpret βo for each population (what does it mean?): Interpret β1 for each population (what does it mean?): Which variable best explains the number of bluehead suckers present in a reach? How did you come to this conclusion? B) Transform the proportion of silt substrate using a square-root transformation, run a regression, and provide the results. Equation βo β1 r r2 Fish vs. silttransformed Did the transformed data provide a better fit to the data than the untransformed data? 3) You are a fisheries manager working on Clear Lake and must monitor the distribution of aquatic macrophytes. Provide a brief description of how you might use each of the following sampling designs to accomplish this task (just focus on the sample locations not different sampling gears). A) Simple random sampling: B) Stratified random sampling: C) Systematic random sampling: In this example, which method do you think is the most appropriate sampling design and why?
