Accuracy Trials

If you want to conduct accuracy trials, you may wish to use a recording interval of 10 to 15 seconds rather than 1 minute because, to locate your accuracy trial in the exported data, you need to have zeros in the file before and after the trial. When using a recording interval of 10 or 15 for an accuracy trial, note the time you begin and have your subject sit or stand still for 30 seconds or more immediately before and immediately after the accuracy trial. The trial will thus be sandwiched by zeros which will allow you to locate it and match up the manual step counts. During accuracy trials, it is helpful to have two observers both using hand held tally counters (available in office supply stores). Two obserrvers with hand-held counters allows them to talk casually with the subject, thus reducing gait changes due to self-consciousness; it also lessens the effect of observer counting errors.

During the trial, LED flashes should be set to a minimal number so observers' counts are not cued by the StepWatch. Have the subject walk at his/her normal pace in an unobstructed area, with the observers walking alongside or following. Be sure the observers are counting only when the leg wearing the StepWatch takes a step (rather than when steps are taken with each leg.) It takes some practice to count accurately because an observer's own walking cadence can interfere with counting the subject's steps. If your accuracy trials are short, any error by the observers will result in a relatively large misrepresentation of the StepWatch accuracy.

When the trial is completed, download the data and export it to a spreadsheet file using the "Export Data..." command in the File Menu. Open the file in your spreadsheet program. Scroll down to the time at which you conducted the trial. If your subject stood still for adequate time before and after the trial, the walking trial will appear as a string of similar values with zeros immediately before and after. Average the observers' manual counts and compare with the StepWatch count.