Data analysis (unfinished)

Coefficient of determination (R²)

…

Chi squared test

Expected value

T test

Quadrat sampling and test of association

• Quadrats are placed inside a defined area in a random arrangement

• Presence or absence of the 2 species is noted in each quadrat

• Sampling process is repeated many times in order togain a representative data set.

Chi-squared test of association

Null hypothesis (h0): there is no significant difference between the distribution of the 2 species (Distribution is random) P (d) > 5%

Alternative hypothesis (h1): There is a significant difference between the distribution of the 2 species P (d) < 5%

Chi² value is (Observed value - Expected value)² / Expected value

• Add all chi² values to use to compare to data.

Degree of freedom = n - 1, n is sample size, n1 + n2 - 2 for independent 2 sample t test, and (r - 1 ) (c - 1) test of independence.