import type { TimeStudyInput, TimeStudyResult } from './types.js';
/**
 * Time Study — Required Number of Observations
 *
 * @formula n = (z × s / (e × x̄))²
 *   where z = z-score for confidence level
 *         s = sample standard deviation
 *         e = accuracy / 100 (fractional)
 *         x̄ = sample mean
 *
 * @reference Barnes, R.M. (1980). "Motion and Time Study".
 * @reference Niebel, B.W. & Freivalds, A. (2003). "Methods, Standards, and Work Design".
 *
 * @throws {RangeError} Observations must have at least 2 elements
 * @throws {RangeError} All observation values must be positive
 * @throws {RangeError} Confidence must be between 0 and 1 (exclusive)
 * @throws {RangeError} Accuracy must be a positive number
 */
export declare function timeStudy(input: TimeStudyInput): TimeStudyResult;
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