Hand disinfection is frequently recommended for prevention of transmission of the rhinovirus that causes the common cold. in particular, hand lotion containing 2% citric acid and 2% malic acid in 70% ethanol (hl+) has been found to have both immediate and persistent ability to inactivate rhinovirus (rv) on the hands in an experimental setting. is hand disinfection effective in reducing the risk of infection in a natural setting? a total of 212 volunteers were assigned at random to either the hl+ group, which used the hand lotion every three hours or after hand washing, and a control group, which was asked to use routine hand washing but to avoid the use of alcohol-based hand sanitizers. here are the data on the numbers of subjects with and without rv infection in the two groups over the 10-week study period: is this an experiment or an observational study? a. experiment. b. observational study23. do the data give good evidence that hand sanitizers reduce the chance of an rv infection? a. yes, it give a good evidence that hand sanitizers reduce the chance of an rv infection. b. no, it doesn't give a good evidence that hand sanitizers reduce the chance of an rv infection. c. we do not have enough evidence.