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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?