At the core of biology and other sciences lies a problem-solving approach called the scientific method. 1  Make an observation. 2  Ask a question. 3  Form a hypothesis, or testable explanation. 4  Make a prediction based on the hypothesis.  Test the prediction.
Xi. Xi is the 14th letter of the Greek alphabet. It is pronounced in Modern Greek, and generally or in English. In the system of Greek numerals, it has a value of 60. Xi was derived from the Phoenician letter samekh. Xi is not to be confused with the letter chi, which gave its form to the Latin letter X.
1 Variance is always measured in squared units. 2  xi{\displaystyle x_{i}} represents a term in your data set. â,  meaning sum, tells you to calculate the following terms for each value of xi{\displaystyle x_{i}}, then add them together.