/**
 * Calculates the sum of an array of numbers.
 */
export declare function sum(numbers: number[]): number;
/**
 * Calculates the mean of an array of numbers.
 */
export declare function mean(numbers: number[]): number;
/**
 * Calculates the mean of an array of numbers.
 */
export declare function average(numbers: number[]): number;
/**
 * Calculates the margin based on a percentage.
 */
export declare function margin(value: number, percentage: number): number;
/**
 * Adds the margin to the value.
 */
export declare function addMargin(value: number, percentage: number): number;
/**
 * Subtracts the margin from the value.
 */
export declare function subtractMargin(value: number, percentage: number): number;
/**
 * Adds the markup to the value.
 */
export declare function addMarkup(value: number, percentage: number): number;
/**
 * Calculates the markup based on a percentage.
 */
export declare function subtractMarkup(value: number, percentage: number): number;
/**
 * Calculates the median of an array of numbers.
 */
export declare function median(numbers: number[]): number;
/**
 * Calculates the mode of an array of numbers.
 */
export declare function mode(numbers: number[]): number[] | null;
/**
 * Finds the minimum value in an array of numbers.
 */
export declare function min(numbers: number[]): number;
/**
 * Finds the maximum value in an array of numbers.
 */
export declare function max(numbers: number[]): number;
/**
 * Returns the minimum and maximum values in an array of numbers.
 */
export declare function minMax(numbers: number[]): [number, number];
/**
 * Returns the difference between two values, expressed as a positive number.
 */
export declare function range(numbers: number[]): number;
/**
 * Returns the standard deviation of an array of numbers.
 */
export declare function standardDeviation(numbers: number[], options?: {
    method: 'sample' | 'population';
}): number;
/**
 * Returns the measure of asymmetry of the probability distribution of an array of numbers. The skewness value can be positive, zero, negative, or undefined.
 */
export declare function skewness(numbers: number[]): number;