I think I'll test my hypothesis about some of my posts being invisible to some people by describing the process we used in our herbicide experiments at the U of Md. If everyone can see this post, then it will probably be safe to conclude that my invisibility hypothesis was incorrect.

We had experimental plots measured out and planted with whatever crop we were testing the herbicide on. The plot was then staked and made into a grid. This comprised several rows of rectangluar areas with a pathway in between each row of rectangles. Each rectangle recieved a different treatment. Some of them had nothing applied to them. These were the controls. The rest of the rectangles had various herbicides applied to them. Some of them had just one herbicide applied to them. Some of them had a combination of herbicides applied to them. We kept careful records of what was applied to each area (and in what quantities), and which areas were the controls.

We then allowed the crops to grow and we used the standard methods of caring for the crops while they grew, except that we only cultivated the pathways in between the rows (using a garden hoe). We left the weeds that grew within the experimental areas alone.

When the crops were ready to harvest, they were cut and left within their rectangle. We then harvested the contents of each rectangle into big plastic lawn and garbage bags, and labled them according to the rectangle they were harvested from.

The crops were stored in a large walk-in refrigerator until they were ready to be sorted. We sorted them bag by bag. First we sorted out the crop and weighed it. Then we sorted the weeds according to category... broad-leafed weeds (dandilions, plantain, etc.), grasses, etc. We weighed each category of weed. We recorded all of the weights of the crops, and different categories of weed.

I wasn't involved in tabulating the results, but they took the information from the records of what was applied to which rectangle of crop (and the controls), and the information from the records of what we measured of the weeds and the crops, and they did their statistical magic to arrive at the results of the experiment.

We had plots at Poplar Hill and the Wye Plantation on the eastern shore of Maryland (USA), and several plots in various locations around Montgomery, Prince Georges, and Carroll Counties in Maryland (USA).