Hand Hygiene

We repeated the experiment with the spider antenna at power level 7 on channel 26.  This time we tested the vertical and horizontal positions.  The boxplot of the horizontal position is not bad, but uninspiring:

In the vertical position, though, it rocks!

The data on the left side is the cleanest that we’ve seen, showing little angular sensitivity: nice nearly horizontal lines for each distance and height out to a distance of .75m (by the way, in the lab we realized that a practical division between .5 and .75 m is probably more useful than .75m versus 1.0m.  Although it’s possible to reach at 1m, it’s not very comfortable).

Let’s break it down a bit more.  Ignoring the difference between height and angle, the data relative to depth looks like this:

There’s still some overlap, so how do the actual distributions overlap?  Here’s a set of fits, assuming the data at each distance are normally distributed:

In the end, it’s going to come down to choosing a threshold.  For that the empirical cumulative density function  at each distance may help.

This graph shows that if we set a threshold of -10 on the RSSI, we’d count about 90% of the .25 m readings, 70% of the .50m readings, and about 5% of the .75 and 1.0m values.  Not quite the 95% accuracy that we want, but we’re certainly moving in the right direction!