Home parties is a sales technique that works because Some products are best sold in person
The products are often sold at a discount
People receive free gifts at the parties
People feel more comfortable buying products in their homes

Industrial engineers who specialize in ergonomics are concerned with designing workspace and devices operated by workers so as to achieve high productivity and comfort. a paper published in this research area reports on a study of preferred height for an experimental keyboard with large forearm-wrist support. a sample of 31 trained typists resulted in an average preferred height of 80.0 cm