A careful review of hospital fatalities due to anesthesia during the last 20 years indicates that the most significant safety improvements resulted from better training of anesthetists  Equipment that monitors a patient' s oxygen and carbon dioxide levels was not available in most operating rooms during the period under review
Ttherefore, the increased use of such monitoring equipment in operating rooms will not significantly cut fatalities due to anesthesia
the reason indicated for the claim that one event caused a second more strongly supports the claim that both events were independent effects of a third event