random acts

Using Math to Find Mr. Right

dihard:

Is he Mr. Right? Is she Miss Right? Don’t leave it to your heart to decide, let the math decide!  Here are three mathematical theories with which to determine if your marriage will last (or should happen at all).

1. The Mathematics of Marriage: In their book, The Mathematics of Marriage, mathematician James D. Murray and psychologist John Gottman describe their use of calculus to study interactions between couples. Using a model Gottman developed in 1979, the pair surveyed 700 newly married couples in King County, Washington in 1992. They analyzed the couples’ 15 minute conversations using a scoring system that assigned a number based on each statement, expression, even pulse rates. The model quantified the ratio of positive to negative interactions during the conversation. They found the magic ratio was 5:1; when the ratio of positive to negative interactions falls below this, a relationship may be in trouble.

These numbers were plotted as a function of time and were used to make predictions as to whether the couple would i) divorce, or ii) stay married a) happily, or b) unhappily. They called this the “Dow Jones for Marital Conversation.” Every 1-2 years until 2004 the couples were asked to complete a questionnaire assessing their marriage and these were compared with the predictions. The prediction of which couples would get divorced was 94% accurate, and typically divorce occurred after 4 years.

2. The 37% Rule: In 1997, Dr. Peter Todd of the Max Planck Institute in Munich described his 37% rule, also known as the secretary rule.  Imagine you have to fill 1 secretarial position and have n # of applicants, ranked from best to worst. Assuming you skip the worst ones (n/e of the applicants where e is the base of the natural logarithm), and you only interview applicants who are better than those you have already interviewed (n/e + 1 is better than all previous n/e interviews), the probability of selecting the best applicant form the pool rounds to 1/e, or around 37%. Hence, you should be able to pick the best secretary after interviewing 37% of the applicants.

If there are about 100 potential “mates” you don’t have to date 37 people to finally meet Mr. Right, #37. Instead, Dr. Todd advises you set your “aspiration level,” what you are looking for in a partner, to a range. Then date only those who are in the top 25% of that range. Your sample size, therefore, is reduced to only 10 dates. One of those should make the cut.

3. The “What are the Chances My Marriage Will Last?” Equation: Garth Sundem, author of GeekLogic created his own equations to determine 1. What are the Chances My Marriage Will Last? 2. Should We Get Married? and 3. How Many Kids Should we Have?

The “What are the Chances my Marriage Will Last? is based on an 11,000 person study by the CDC that explored factors that help and hurt a marriage’s chances of working.

Here’s the equation:

where
A= Her age at time of marriage
E=Current combined years of post-high-school education
K= Number of kids from this marriage
R= How religious is the couple (1-10 with 10 being “the Pope”)
D= Combined number of divorces of couple’s parents
P= Combined previous marriages
T= Years at which you are computing the chances
H._E.A. = % chance of Happily Ever After

But don’t worry about calculating it out yourself. Over at Political Calculations, you can type in your personal data and it spits out the probability you and your partner will still be married at a given year of anniversary.