old_contents: 'use strict';
  
  // MODULES //
  
  var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
  var isPositive = require( '@stdlib/assert/is-positive-number' ).isPrimitive;
  var isnan = require( '@stdlib/assert/is-nan' );
  
  
  // MAIN //
  
  /**
  * Validates parameters.
  *
  * @private
  * @param {number} mu - mean
  * @param {PositiveNumber} b - shape parameter
  * @returns {(Error|null)} error or null
  *
  * @example
  * var err = validate( 1.0, 2.0 );
  * if ( err ) {
  *     throw err;
  * }
  */
  function validate( mu, b ) {
  	if ( !isNumber( mu ) || isnan( mu ) ) {
  		return new TypeError( 'invalid input argument. `mu` must be a number primitive and not `NaN`. Value: `' + mu + '`.' );
  	}
  	if ( !isPositive( b ) ) {
  		return new TypeError( 'invalid input argument. `b` must be a positive number. Value: `' + b + '`.' );
  	}
  	return null;
  } // end FUNCTION validate()
  
  
  // EXPORTS //
  
  module.exports = validate;
  
new_contents: 'use strict';
  
  // MODULES //
  
  var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
  var isPositive = require( '@stdlib/assert/is-positive-number' ).isPrimitive;
  var isnan = require( '@stdlib/assert/is-nan' );
  
  
  // MAIN //
  
  /**
  * Validates parameters.
  *
  * @private
  * @param {number} mu - mean
  * @param {PositiveNumber} b - scale parameter
  * @returns {(Error|null)} error or null
  *
  * @example
  * var err = validate( 1.0, 2.0 );
  * if ( err ) {
  *     throw err;
  * }
  */
  function validate( mu, b ) {
  	if ( !isNumber( mu ) || isnan( mu ) ) {
  		return new TypeError( 'invalid input argument. `mu` must be a number primitive and not `NaN`. Value: `' + mu + '`.' );
  	}
  	if ( !isPositive( b ) ) {
  		return new TypeError( 'invalid input argument. `b` must be a positive number. Value: `' + b + '`.' );
  	}
  	return null;
  } // end FUNCTION validate()
  
  
  // EXPORTS //
  
  module.exports = validate;
  
subject: Fix parameter description