sample size and variance tutorial

# sample size and variance tutorial - : ?Howmanytreesinthis...

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ENVS 1500 Tutorial – Excel: Sample size and variance What percentage of this field has little bluestem grasses? How many trees in this forest are red maples? Ecologists use systematic sampling methods to answer these types of questions. It is generally not feasible to count all of the individuals of a particular species, so ecologists developed sampling methods where they sample a subset of the population. The sampling method used, and the amount of effort put into the sampling, are important features of study design. The goal of today’s tutorial is to understand the very basics of descriptive statistics: 1) to understand the concepts of sample size, mean (or average) and measures of variability using a dataset; and 2) to become familiar with the software program Excel. Background terminology: Sample size (n) – the number of samples collected (e.g., the number of quadrats plots used to sample big bluestem grasses). The larger the sample size, the more robust the dataset. Mean (aka average) – “...is found by taking all of the scores, adding them up, and dividing by the number of scores .... the mean is the sum of all scores, divided by n .” (Lindner 1979).

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• Fall '13
• Lindner

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