When scientists have made many observations and collected existing data, they suggest a possible explanation for what they have seen and recorded. this explanation, called a hypothesis, is a statement that both explains their observations and data and can be tested. hypothesizing is a very important step in scientific investigations. a statement is testable if evidence can be collected that either supports or disproves it. a hypothesis may be shown to be wrong, but it can never be proved true beyond all doubt. it can only be supported by evidence. at any time, new data might indicate that a previously accepted hypothesis does not hold true in all instances. scientists often must refine and revise their original hypotheses—or even discard them—as they uncover new evidence. to test a hypothesis, scientists make a prediction that logically follows from the hypothesis. a prediction is a statement made in advance that states the results that will be obtained from testing a hypothesis, if the hypothesis is true. a prediction most often takes the form of an “if-then” statement. a hypothesis is often tested by carrying out an experiment. experimenting is the process of testing a hypothesis and its predictions by gathering data under controlled conditions. Question
1- What key vocabulary terms are contained in this passage?

2- give the meaning of these terms.