Monday, June 30, 2014

Dropping incomplete plots

Starting today, you'll be able to drop incomplete plots from a cruise.  When you go to a cruise page on the website, you'll see a new orange button "Drop incomplete plots" that shows up after you've completed at least one plot.

A word of warning though - you may bias your sample by dropping plots.  Unless you're dropping plots in a completely random or completely systematic manner, you are likely biasing your sample.

So if you drop every third plot, your sample will be unbiased (although you may not hit your target accuracy and confidence for the cruise).

However, if you drop all the wet plots, the plots furthest from your truck, or plots with bees on them, you are biasing your sample.  In that case, the estimates derived from your cruise data would be for a population that did not include the areas you chose not to sample.  This is likely not what you want!

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