Estimates produced include acreages with associated standard errors. Many estimates are not considered reliable enough to recommend their use for making decisions. An indication is given of the reliability of each estimated acreage in the summary tables included in this appendix. The standard error of each entry expressed as a percentage of the entry (SE%) is below each estimate. Reliability can be stated generally as "we are 68 percent confident that the true value is within the interval constructed by adding to and subtracting from the entry the SE%/100 times the entry." For example, if an entry is one million acres and the SE% is 20, then we are 68 percent confident that the true value is between 800,000 and 1,200,000 acres. An equivalent statement for 95 percent confidence can be made by adding and subtracting twice the amount to and from the entry. Therefore, a large SE% indicates low reliability, if any, in the estimate.

This discussion on reliability is meant to aid in interpretation of the study results. It was expected that only certain estimates would be precise enough to be meaningful. However, all entries are included in the summary table for additivity and ease of comparison.

Estimates for the mid-1970's, the mid-1980's and change during the period were produced for categories described in Appendix A. These estimates are summarized in Table 1 of Appendix B. Totals for columns are estimates of total acreage by category for the mid-1980's. Row totals (the extreme right column) are estimates of total acreage by category for the mid-1970's. Entries are interpreted as in the following examples (all from the ninth row or column of Table 1):

Table 1.
Area, in thousands of acres, by surface area classification.

Table 2.
Area, in thousands of acres, by selected surface area groups.

4,842,400 acres classified as palustrine emergent in the mid-1970's were again classified palustrine emergent in the mid-1980's.

Pitcher Plants
PALUSTRINE EMERGENT
NORA MURDOCH

208,700 acres are classified as palustrine emergent in the mid-1970's had changed to agriculture by the mid-1980's.

156,800 acres classified as palustrine scrub/shrub in the mid-1970's had changed to palustrine emergent by the mid-1980's.

The estimate of palustrine emergent area in the mid-1970's is 5,459,700 acres.

The estimate of palustrine emergent area in the mid-1980's is 5,829,600 acres.

The estimate of net change in palustrine emergent area in the mid-1970's and the mid-1980's is 369,900 acres.