## WW I wAym

where n sample size (number of sample plots required for monitoring), ta value of Student's t statistic for a = 0.05 (implying a 95% confidence level), Ns total number of strata designed, N number of potential sample units (permanent sample plots in the stratum level), S. standard deviation in stratum i, A permissible error in the mean, C. cost of selecting a sample plot in stratum I, Wi = N/N. The number of plots shall be allocated among the strata:

f n n = n ■ pt andpt = )/1 Wt s^C, where n. is the number of samples to be allocated in stratum i.

The allowable error is a value on per-plot basis estimated as ±10% of the mean biomass carbon stock per plot. The sample size determined during the project development phase could be modified during the project monitoring phase if new information necessitating a change in sample size becomes available.

Sampling error The term sampling error is used to express the difference between a population mean and the mean of a sample drawn from that population. This error is caused by sampling. If no error exists, the sample mean will be exactly equal to the population mean. When plot-level measurements are scaled up, sampling errors occur because conditions across the larger area vary whereas measurements are made only at the sample locations. The average conditions within the selected sample plots seldom coincide exactly with the average conditions within the entire area of interest. Sampling errors (using random sampling designs and unbiased estimators) are only random and can be reduced by increasing sample size. The relation between sampling error, population variance and sample size is generally known: increasing sample size leads to higher precision, and heterogeneous populations (forests with diverse vegetation) require a larger sample size to obtain the desired precision.

## Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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