Sports Prediction Glossary

A backtest is a method of testing a prediction strategy using historical data to see how it would have performed in the past. It involves applying your strategy rules to past games and calculating the theoretical results.

Bankroll management is the practice of properly sizing bets relative to your total betting funds to minimize risk of ruin. Common strategies include flat betting (same amount each bet) or percentage-based betting (1-3% per bet).

Closing Line Value measures whether you got better odds than the final (closing) line. Consistently beating the closing line is considered a strong indicator of long-term profitability, as closing lines are typically the most accurate.

Expected Value (EV) is the average amount you can expect to win or lose per bet over the long term. Positive EV (+EV) bets are mathematically profitable over time. EV is calculated by multiplying each outcome's probability by its payout and summing the results.

The favorite is the team or player expected to win according to oddsmakers. Favorites have negative moneyline odds (e.g., -150) and give points on the spread (e.g., -5.5). Betting favorites means accepting lower payouts for higher win probability.

Historical data in sports prediction refers to past game results, statistics, odds, and other information used for analysis and backtesting. Quality historical data is essential for testing prediction strategies.

Juice, also called vigorish or vig, is the commission the sportsbook takes on bets. Standard juice is -110 on both sides, meaning you must bet $110 to win $100. Lower juice (-105) is more favorable to bettors.

Line movement refers to changes in odds or point spreads from when they open until game time. Lines move due to betting action, injury news, or other factors. Tracking line movement can indicate where sharp money is going.

A moneyline bet is a wager on which team will win the game outright, regardless of the margin. Odds are expressed as positive (underdog) or negative (favorite) numbers indicating the payout ratio.

An over/under bet, also called a totals bet, is a wager on whether the combined score of both teams will be over or under a number set by oddsmakers. For example, if the total is set at 215.5, you bet whether the final combined score will be higher or lower.

A parlay is a single bet that combines multiple individual wagers. All selections must win for the parlay to pay out. Parlays offer higher potential payouts but lower probability of winning. A 3-leg parlay requires all 3 picks to be correct.

A prop bet (proposition bet) is a wager on a specific outcome within a game that doesn't directly relate to the final score. Examples include player performance props like "LeBron James over 25.5 points" or game props like "first team to score."

ROI in sports prediction measures the profit or loss as a percentage of the total amount wagered. An ROI of 5% means for every $100 wagered, you would profit $5 on average. Positive ROI indicates a profitable strategy.

Sample size is the number of bets or games analyzed in a backtest or strategy evaluation. Larger sample sizes provide more reliable results. A minimum of 100-500 bets is typically recommended for meaningful statistical significance.

Sharp money refers to bets placed by professional or highly successful bettors. Sharp bettors typically have access to better information and analysis. Line movements caused by sharp money are considered more significant than public betting trends.

The spread (also called point spread) is the predicted margin of victory set by oddsmakers. A team favored by -7 must win by more than 7 points to "cover the spread," while the underdog at +7 can lose by up to 6 points and still cover.

The underdog is the team or player expected to lose according to oddsmakers. Underdogs have positive moneyline odds (e.g., +150) and receive points on the spread (e.g., +5.5). Betting underdogs offers higher payouts but lower win probability.

A unit is a standardized bet size used for bankroll management. Typically 1-2% of your total bankroll. If your bankroll is $1,000 and 1 unit = 1%, then 1 unit = $10. Using units helps track performance consistently regardless of bankroll size.

A value bet occurs when you believe the true probability of an outcome is higher than what the odds imply. For example, if odds suggest a 40% chance but your analysis shows 50%, that's a value bet with positive expected value.

Win rate is the percentage of bets won out of total bets placed. A 55% win rate means winning 55 out of every 100 bets. Note: win rate alone doesn't determine profitability - odds and bet sizing also matter.