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.
E(X) = Î¼x = Ï [ xi * P(xi) ] where xi is the value of the random variable for outcome i, Î¼x is the mean of random variable X, and P(xi) is the probability that the random variable will be outcome i. Example 1. In a recent little league softball game, each player went to bat 4 times.