Alpha symbol α

• Statistics: α is the significance level of a hypothesis test, the accepted risk of a false positive (a Type I error). α = 0.05 is a common choice. Cronbach’s α measures the reliability of a survey scale.
• Geometry and trig: α, β and γ name the angles of a triangle.
• Physics: alpha particles are helium nuclei; α also stands for angular acceleration and for the fine-structure constant.
• Finance: alpha describes an investment’s return relative to a benchmark.
• Software: an alpha release is an early, incomplete test version that comes before the beta.
• Biology and chemistry: the α-helix in proteins, α-tocopherol (a form of vitamin E).

• a (Latin a): in many fonts α and a look alike, especially in italics. In formulas, mixing them up changes the meaning, so copy the Greek letter.
• Α (capital alpha) is visually identical to the Latin capital A in most fonts but is a different character. Look-alike letters like this have been used in spoofed web addresses, which is one reason browsers show some international domain names in an encoded form.
• ∝ (proportional to) looks like an open alpha: y ∝ x means y is proportional to x. In LaTeX it is \propto.

In chemical and biological names, style guides differ: α-linolenic acid and alpha-linolenic acid are both correct. Pick one form and use it throughout a document.

• Word: in an equation (Alt+=), type \alpha and press space.
• LaTeX: \alpha. There is no \Alpha command, because the capital is simply A in upright type.
• Mac: open the Character Viewer with Control+Command+Space and search “alpha.”
• iPhone and Android: add the Greek keyboard; α is where A is on a US keyboard.
• Excel: α is only a label in a sheet, but functions such as =CONFIDENCE.NORM(0.05, sd, n) take the alpha value as a number.