"among postmenopausal women, the lower the overnight production of melatonin - a brain hormone secreted at night, esp. during darkness- the higher the incidence of breast cancer"
which is the dependent variable and which is the independent variable. why?In a scientific experiment which is the independent and dependent variable?
The independent variable is the variable that you change (the amount of melatonin). The dependent variable is the variable that changes in response to the independent variable (incidence of breast cancer). The dependent variable DEPENDS upon the value of the independent variable.In a scientific experiment which is the independent and dependent variable?
The answer depends on exactly how the researchers designed the experiment. Certainly one independent variable is "Postmenopausal Women", or more likely the menopausal status of women chosen for the research (the other group being "Premenopausal Women"). If the researchers further divided the women into "High Melatonin Producers" and "Low Melatonin Produces" that would add a secondary level of independent variables to both groups of women. If that is the case, the presence or absence of breast cancer would be the dependent variable which, of course, is expressed as nominal or catagorical level data.
The easiest way to keep the independent and dependent variables apart is to note which one generates the data that the researcher is recording. Mind the "D's"; Dependent variables produce Data.
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