Investing your money: the long and the short of it

Sometimes we want to see how people change over time, as in studies of human development and lifespan. When we test the same group of individuals repeatedly over an extended period of time, we are conducting longitudinal research. Longitudinal research is a research design in which data-gathering is administered repeatedly over an extended period of time. For example, we may survey a group of individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again...

Equity theory explains how our sense of fairness influences the dynamics of close relationships. Rooted in social psychology, the theory posits that individuals evaluate fairness by comparing the ratio of their contributions to the rewards they receive. Relationship satisfaction is highest when these ratios are perceived as balanced between partners, promoting mutual reciprocity and a sense of justice.Equity vs. Equality in RelationshipsEquity is distinct from equality. Fairness does not...

Compound interest describes how an investment grows when interest is added not only to the initial amount but also to previously earned interest. With a 4% annual compound interest rate, each year’s balance becomes 1.04 times the previous year’s amount. This growth forms a geometric sequence, where the common ratio of 1.04 represents the consistent multiplier applied to each term.To analyze whether an infinite sum of such terms reaches a finite value or grows indefinitely, mathematicians use...