Data Analysis & Reporting Flashcards

A forester measures DBH for 50 trees and gets a mean of 18 cm with a standard deviation of 4 cm. What is the coefficient of variation (CV)?

Answer: 22.2%

CV = (standard deviation / mean) × 100 = (4/18) × 100 = 22.2%.

Which sampling design is most appropriate when a forest stand has clearly distinct zones of high-density and low-density trees?

Answer: Stratified random sampling

Stratified random sampling divides the population into homogeneous strata, improving precision when distinct zones exist.

In a forest inventory report, the term 'basal area per hectare' is expressed in which units?

Answer: m²/ha

Basal area per hectare is expressed in m²/ha, representing the cross-sectional area of tree stems at breast height per unit area.

A forester uses a relascope with a basal area factor (BAF) of 10. She tallies 14 'in' trees at one point. What is the estimated basal area per hectare?

Answer: 140 m²/ha

Estimated basal area = number of 'in' trees × BAF = 14 × 10 = 140 m²/ha.

Which statistical test is used to compare the means of two independent groups of tree height measurements to determine if they differ significantly?

Answer: Independent samples t-test

An independent samples t-test compares means from two unrelated groups to test for statistically significant differences.

What does the 'p-value' in a statistical test represent?

Answer: The probability of observing results at least as extreme as those found, given the null hypothesis is true

The p-value is the probability of obtaining a result as extreme as the observed one if the null hypothesis were true.

In forest inventory data, a positively skewed distribution of tree volumes would indicate that:

Answer: Most trees are small or average-sized with a few very large outliers

Positive skew means the tail extends to the right, indicating most observations are lower with a few very high values.