# Unusual (to me) Phrasing of Power Analysis Objective; Interpretation Requested

Cross Validated Asked by EmmettCC on December 15, 2020

I am reading a field biology manual that is directing me to do a power analysis, and I find the phrasing very confusing. It says:

Determine sampling requirement to be 80% confident you are within 10% of the objective. (More concretely: how many survey plots do I need to be 80% confident of whether I am within 10% of having 65 trees per hectare?)

It’s phrased like a power analysis, but is confidence a synonym for power, and is being with 10% an indication of the alpha?

*Can anyone suggest what the statement means mathematically (e.g., B = 0.8)?
*Can anyone recommend an R package for this?

You are asked to find out how many survey plots are needed to make the confidence interval (CI) equals 56.5 ~ 71.5 with the confidence level (CL) equals 80%. In other words, how many survey plots are needed in order to be able to claim with 80% confidence that there are 56.5~71.5 trees per hectare on average.

Answered by user295357 on December 15, 2020

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