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.
retrospective study, a study in which a search is made for a relationship between one phenomenon or condition and another that occurred in the past (e.g., the exposure to toxic agents and the rate of occurrence of disease in the exposed group compared with a control group not exposed). study. a scholarly examination.