ICAR AICE-JRF/SRF Forest Inventory & Sampling Design: practice questions

Question 1 · medium

Precision and accuracy differ because:

1. Precision depends on bias, while accuracy depends only on the number of plots
2. Precision applies to totals only, while accuracy applies to per-hectare means only
3. Precision measures repeatability of estimates, while accuracy also depends on bias
4. Precision is measured in hectares, while accuracy is measured in cubic metres

Question 2 · medium

A sample of plots has a mean of 160 m³/ha and a standard deviation of 20 m³/ha. What is the coefficient of variation?

1. 8.0 per cent
2. 1.25 per cent
3. 800 per cent
4. 12.5 per cent

Question 3 · hard

In two-stage sampling, primary units of very unequal size are often selected:

1. With probability proportional to their size
2. With equal probability regardless of size
3. Only if they are smaller than the average unit
4. Only if they lie next to a road or river

Question 4 · hard

In metric angle-count sampling with BAF 4 m²/ha, what is the limiting distance for a tree of 50 cm dbh?

1. 25.0 m
2. 12.5 m
3. 6.25 m
4. 50.0 m

Question 5 · hard

A plot centre falls 5 m inside the forest boundary. What is the correct procedure?

1. Move the plot inward until the whole circle lies inside the forest boundary
2. Discard the plot and choose a new random point well away from the boundary
3. Keep the plot where it falls and use a boundary correction such as the mirage method
4. Double the plot radius so that the plot area inside the forest stays the same as for interior plots

Question 6 · medium

In continuous forest inventory, V1 = 190, V2 = 220, mortality = 10 and cut = 20 m³/ha over the period. What is the gross growth including ingrowth?

1. 60 m³/ha
2. 30 m³/ha
3. 50 m³/ha
4. 0 m³/ha

Question 7 · hard

Why does remeasuring the same permanent plots estimate change more precisely than comparing two independent sets of temporary plots?

1. Permanent plots are always larger than temporary plots and so contain more trees of every size class
2. Temporary plots cannot be measured with the same instruments as permanent plots
3. Permanent plots are placed only in stands of average growth and so vary less
4. Positive correlation between successive measurements on the same plot cancels much of the variation

Question 8 · hard

Why are changes to a national inventory's plot design or definitions made with care and often with an overlap period?

1. Changes are forbidden by FAO rules for every country that reports to the global assessment and can never be made
2. Changes can break the time series, so differences may reflect method rather than real change
3. Changes would make the inventory cheaper, which reduces its funding from government
4. Changes always increase the estimated growing stock by a fixed percentage each time

Question 9 · medium

Adaptive cluster sampling is useful for inventorying a non-timber species that is:

1. Rare and clumped
2. Common and evenly spread
3. Planted in uniform rows
4. Found only in nurseries

Question 10 · medium

An inventory report gives a district volume to the nearest cubic metre but no sampling error. What is the main criticism?

1. Without errors and methods the precision cannot be judged and the figures look more exact than they are
2. Volumes should always be reported to the nearest litre for consistency with sawmill records kept at the depot
3. Reports should never contain volumes; only tree counts are acceptable in inventory
4. District figures are confidential and should not appear in any inventory report