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Shannon Entropy CalculatorCompute Shannon entropy H = -Σ pᵢ·log₂(pᵢ) from a probability distribution. Supports bits, nats and dits, plus max entropy and efficiency.
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Confidence Interval for Difference of Two Means CalculatorCompute a confidence interval for the difference between two independent sample means using the Welch t-method. Enter means, SDs, sizes and confidence level.
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Confidence Interval for Difference of Two ProportionsCompute a confidence interval for the difference between two sample proportions (p̂₁−p̂₂) at 90%, 95%, or 99% using the normal approximation.
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Cohen's Kappa CalculatorCalculate Cohen Kappa (κ) for inter-rater agreement from a 2x2 table. Get observed and expected agreement and interpret reliability instantly.
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Permutations and Combinations (Sample Selection) CalculatorCompute combinations, permutations, with/without replacement, factorial, even/odd and circular permutations. All four sample-selection cases in one calculator.
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Permutations with Replacement CalculatorCalculate permutations with replacement P^R(n,r) = n^r — the number of ordered sequences of r items drawn from n objects when order matters and repeats are allowed.
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Combination with Replacement CalculatorCompute combinations with replacement (multichoose): the number of ways to choose r items from n types, unordered, with repetition allowed. Free, instant.
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Sample Variance CalculatorCalculate sample variance (s²) and standard deviation from a data set. Uses the n−1 unbiased formula, with mean and sum of squared deviations.
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Dating Theory (Optimal Stopping) CalculatorUse the 37% rule (optimal stopping / secretary problem) to find how many dates to reject before committing. Enter your pool size and get the answer.
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Poker Pot Odds CalculatorCalculate poker pot odds and the minimum equity you need to call profitably. Enter the current pot and the bet you must call to get instant percentages.
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Poker EV CalculatorCalculate the expected value (EV) of a poker decision from your win probability, the amount you win, and the amount you lose. Free and instant.
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Fisher's Exact Test Calculator (2x2)Compute the exact p-value for a 2x2 contingency table using Fisher exact test. Get the hypergeometric probability and two-sided p-value instantly.
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Matched Betting CalculatorFree matched betting calculator. Enter back odds, stake, lay odds and exchange commission to get your optimal lay stake, liability and locked-in profit.
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Mean Absolute Deviation (MAD) CalculatorCalculate the Mean Absolute Deviation (MAD) of any data set instantly. Enter your numbers to find the average distance from the mean, plus the mean and count.
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Two Dice Probability CalculatorCalculate the probability of rolling a given sum with two six-sided dice. Find exact, less-than, or greater-than odds out of 36 outcomes instantly.
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Specificity CalculatorCalculate specificity (true negative rate) from TN and FP counts. Free, instant Specificity = TN / (TN + FP) calculator with worked example.
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Sensitivity CalculatorCalculate sensitivity (true positive rate) from true positives and false negatives. Free online tool for diagnostic tests and ML classifiers.
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Probability Fraction CalculatorCalculate probability from favorable and total outcomes. Get the decimal probability, percentage, and odds in favor instantly with this free tool.
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Permutation with Repetition CalculatorCalculate permutations with repetition using P = n^r. Enter the number of items (n) and selections (r) to find total ordered arrangements instantly.
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OR Probability CalculatorCalculate P(A or B) using the addition rule: P(A) + P(B) − P(A and B). Find the probability that at least one of two events occurs.
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Permutation without Repetition CalculatorCalculate permutations without repetition P(n,r) = n!/(n−r)!. Find the number of ordered arrangements when selecting r items from n distinct items.
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Moneyline Odds CalculatorConvert American moneyline odds into payout, profit, decimal odds and implied probability. Enter your stake and odds (e.g. +150 or -200) instantly.
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Fractional Odds CalculatorConvert UK fractional betting odds (e.g. 5/2) into total payout, profit, implied probability and decimal odds for any stake.
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False Positive Rate CalculatorCalculate the false positive rate (FPR) from false positives and true negatives. FPR = FP / (FP + TN) = 1 - specificity. Free online tool.
