In this study 100 groups of five participants were used to discover problems with an interface. The study did indeed find that the mean percentage of problems discovered across all 100 groups was about 85%. However, this figure has 95% confidence level and a margin of error of Â±18.5%.
Keelboats were generally built in Pittsburgh, Pennsylvania and it was here that Meriwether Lewis commissioned the boat used by the Corps of Discovery. The keelboat used by the Corps was sketched by Clark in his journal. It was 55 feet long and 8 feet wide, with a 3- to 4-foot draft. For propulsion it had a 32-foot sailing mast, 22 oars, a rudder, and a tiller for steering. Protection against hostile encounters were a swivel cannon on the bow and two smaller guns called blunderbusses.
the year ad 700, they were sailing boats that were better than any others on the ocean . The boats they built, called knarrs (kuh-NARS), were used mostly for trading . These boats were up to 16 .5 meters (54 ft) long and 4 .5 meters (15 ft) wide . Because they were flat bottomed, the knarr boats could carry heavy loads . They were also stable and could travel safely across the open ocean . Viking explorers were willing to travel into the unknown to claim new lands and seek adventure . They were also the first Europeans to visit North America . Vikings also built warships known as longships .