Quick Answer. In some rare cases, excessive stress causes bleeding between periods. It is more common that another condition is responsible, such as pregnancy, polycystic ovary syndrome, infection, pelvic inflammatory disease or side effects of medication, according to WebMD.
Using the scientific method, you can repeat the experiment to find out for yourself whether or not the other researcher's assertions are true. This is a key factor that separates science from dogma! The other important part of scientific research is that a hypothesis must be falsifiable. A falsifiable hypothesis or theory is one where an experiment or another discovery can prove it to be wrong, untrue, and false.
One of the key factors in developing and testing scientific theories is the identification and operational definition of the variables that describe phenomena observed in the real world. Variables are measured in a research study, and they can have more than one value. There are several types of variables of interest to the researcher. Independent variables are stimuli that are manipulated in order to determine their effect on the value of dependent variables.