/**
 * @returns Average of the array of numbers
 *
 * @example
 *
 * _average([1, 2, 3, 4])
 * // 2.5
 */
export declare function _average(values: number[]): number;
/**
 * Same as _average, but safely returns null if input array is empty or nullish.
 */
export declare function _averageOrNull(values: number[] | undefined | null): number | null;
/**
 * valuesArray and weightsArray length is expected to be the same.
 */
export declare function _averageWeighted(values: number[], weights: number[]): number;
/**
 * @example
 *
 * _percentile([1, 2, 3, 4], 50)
 * // 2.5
 *
 * _percentile([1, 2, 3], 50)
 * // 2
 *
 * _percentile([1, 2, 3], 100)
 * // 3
 */
export declare function _percentile(values: number[], pc: number): number;
/**
 * A tiny bit more efficient function than calling _percentile individually.
 */
export declare function _percentiles(values: number[], pcs: number[]): Record<number, number>;
/**
 * @example
 *
 * _median([1, 2, 3])
 * // 2
 *
 * _median([1, 2, 3, 4])
 * // 2.5
 */
export declare function _median(values: number[]): number;