What is the meaning of ΣX² in a frequency distribution?

• A. The sum of squared X values
• B. The square of the sum of X values
• C. The sum of X values
• D. The product of X and frequency squared

Answer: (A)

ΣX² means adding up the squares of the X values. In other words, take each observation’s X, square it, and sum those squared values across all observations. This is different from squaring the sum (which would be (ΣX)²) and from simply summing the X values (which is ΣX). In a frequency distribution, you might see ΣfX², where you weight each X by its frequency and sum the squared values accordingly. Example: for data 2, 4, 3, ΣX² = 2² + 4² + 3² = 4 + 16 + 9 = 29. This quantity is used in calculations like variance because it captures the squared deviations from zero.