Data Analysis & Reporting Flashcards

A forester finds that the correlation coefficient (r) between tree age and height is 0.87. What percentage of variation in height is explained by age?

Answer: 75.7%

The coefficient of determination R² = r² = 0.87² = 0.757, meaning 75.7% of height variation is explained by age.

Which type of error occurs when a forester concludes that there IS a significant difference between two forest stands when in reality there is NOT?

Answer: Type I error (false positive)

A Type I error (false positive) is rejecting a true null hypothesis — incorrectly concluding a difference exists.

In forest carbon accounting, the term 'above-ground biomass' (AGB) most commonly excludes which of the following?

Answer: Roots

Above-ground biomass includes stems, branches, and foliage but excludes roots, which are counted as below-ground biomass.

A forester wants to compare species diversity across five different forest stands. Which index accounts for both species richness AND evenness?

Answer: Shannon-Wiener diversity index

The Shannon-Wiener index (H') incorporates both the number of species (richness) and the proportional abundance of each species (evenness).

In a multiple regression model predicting timber volume, a high Variance Inflation Factor (VIF > 10) for a predictor variable indicates:

Answer: Severe multicollinearity — that predictor is highly correlated with other predictors

A VIF above 10 signals severe multicollinearity, meaning that predictor's variance is largely explained by other predictors, making coefficients unstable.

Systematic sampling in a forest inventory involves:

Answer: Placing plots at fixed, equally spaced intervals across the area

Systematic sampling places sample units at equal intervals (e.g., every 200 m on a grid), providing good spatial coverage with minimal effort.

A forester uses allometric equations to estimate tree biomass from DBH measurements. The term 'allometric' refers to:

Answer: Relationships between different body measurements of an organism that follow a power function

Allometric equations describe proportional relationships between biological dimensions (e.g., DBH and biomass) typically expressed as power functions.