Lab - Describing a Population Flashcards
Sampling
To demonstrate the power of quantitative description in ecology
Population
A group of individuals of a species living at the same time and place
Sample
A set of individuals that represent a population that is too large to fully interview
Bias
Sampling flaws that overrepresent individuals of one type and underrepresent others
Statistic
a composite numerical description which conveys information about the population in a more concise form
Average / mean
The representation of a typical individual. Can be misleading because the “typical” fish might not even be represented in the population
Median
the individual ranked at the 50th percentile when all data are arranged in numerical order
Mode
The most commonly observed statistic in a sample
Histogram
a simple graphic representation of the way individuals in the population vary
Normal distribution
A bell shaped curve of distribution where the extremes are at either end and the most common forms fall in great amounts
Parametric statistics
Models and tests based on normal distribution
Non-parametric tests
If the histogram of variation is lopsided, has more than one peak, or is too broad or too narrow, then parametric tests cannot be used.
Sample size
The larger the sample size, the more closely represented the population is.
n= size of the sample N= size of the entire population
Standard deviation
A statistic that measures the amount of variation around the mean
s= the standard deviation of the sample o= the standard deviation of the whole population
The variance
The square of the standard deviation. S^2 = sample variation and o^2 is the population variance. Calculation of the variation is based on the difference between each observation and the mean.
