A fire department is evaluating a new training program to improve firefighters' response times. They compared fire stations in LA, Dallas, and Miami that used the traditional program to fire stations in San Francisco, Houston, and Chicago that implemented the new program. Both groups of stations recorded their firefighters' average response time (in seconds) to emergency drills. ID Compared To Number of Stations Average Response Time (secs) LA (Traditional) San Fran (New) 17 28 San Fran (New) LA (Traditional) 19 32 Dallas (Traditional) Houston (New) 14 27 Houston (New) Dallas (Traditional) 12 29 Miami (Traditional) Chicago (New) 18 31 Chicago (New) Miami (Traditional) 16 34 What was compared? [ Select ] What baseline characteristics were controlled for? [ Select ] Was random assignment used? [ Select ] What kind of study design did this study use? [ Select ] On average, how does the usage of the new program affect average response time? [ Select ] Evaluate the internal validity of the study? [ Select ] Firefighters in San Fran, Chicago, and Houston are on average older than firefighters in LA, Dallas, and Miami, and it is known that reaction time decreases with age. How does this information impact your interpretation of the results? [ Select ]