In scientific research, an attribute is a characteristic of something (such as a person or object). A variable is a set of attributes. An attribute is the specific value of that variable. In sociology, for example, a common variable is gender, and the attributes are male and female (and perhaps transgender or other categories in some experiments). The variable of whether someone agrees with a statement is also common in sociology. The attributes of this variable can be defined differently and could include a five-point scale that includes strongly agree, agree, neutral, disagree, and strongly disagree. Age is another common variable, and the attributes could be under 18, 18-40, 41-60, and 61-80. The attributes can be defined differently in different experiments. 

Scientific inquiry tries to avoid pitfalls that produce errors in nonscientific inquiry by reducing what is called "noise." This concept refers to uncontrolled factors (other than the independent variable) that affect the dependent variable. To control these types of errors, the researcher must try to eliminate as many outside factors as possible. For example, if a researcher is testing the effect of a rehabilitation program on the elderly, he or she should choose subjects (people in the experiment) who are from similar socio-economic groups to control for the factor of socio-economic status (SES) in the experiment. In addition, researchers try to control for error by repeating experiments and using a large sample. The larger the sample size, the more likely the experimenter is to avoid having a lot of noise in an experiment because the larger number of samples will control for this noise. For example, if there is a large sample size in the experiment with the older people described above, having subjects from a lower SES group might be canceled out by having other subjects with a higher SES.