Acres to Hectares Conversion. There are 0.404685642 hectares in an acre. In other words, it is about 40 percent of a hectare. To find out how many hectares in acres, multiply by the conversion factor or instead, use the converter below. Acre is an imperial and US customary area measurement unit which equals to 43560 square feet.
intervention study. testing an hypothesized epidemiological cause-effect relationship by intervening in a population and modifying a supposed causal factor and measuring the effect of the change.
What is the difference between prospective and retrospective studies? A: A prospective study monitors the outcome within a study group and relates it to suspected risk or preventive factors. A retrospective study relates the outcome to risk and preventive factors present prior to the start of the study. Prospective studies involve larger study groups than retrospective studies.