Quantitative research precisely counts behaviors, knowledge, opinions or attitudes by measuring quantities or amounts. It aims to answer questions about how much, how often, how many, when, who, etc. There are two main types: inferential research, which makes inferences from specific data to general conditions; and experimental research, where the researcher controls variables to determine or predict outcomes. Key terms are dependent variables, which depend on another, and independent variables, which occur before dependent variables. Simulation is also used as an alternative to experiments by creating artificial environments that resemble real-world settings.