# How to compare a single (counted) value to a mean for statistical significance in R

I am working on a project estimating salmon escapement through visual spawner surveys. We conducted weekly surveys and counted the number of individuals we observed. These numbers were used in an Area-under-the-curve model to estimate the number of salmon present across the entire survey period. This model provides a cumulative estimate (single value) with no mean or sd.

I want to compare the current year's estimate (374.43) to the average escapement across previous years' estimates (n=19, mean=432.2179, sd=632.0642) to determine if my escapement estimate for this year significantly differed from historical data for a given stream.

• I can tell you right now, if your mean is 400 and the sd is 600, 374 is not "out of the ordinary" :) Commented Mar 20 at 4:04
• Are you perhaps interested in a prediction interval? So given the data you've already collected, it's an interval for which 95% of "new" values should be contained in. Commented Mar 20 at 4:05