text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2018 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  'use strict';
  
  // MODULES //
  
  var isNumber = require( '@stdlib/assert-is-number' ).isPrimitive;
  var isObject = require( '@stdlib/assert-is-plain-object' );
  var isString = require( '@stdlib/assert-is-string' ).isPrimitive;
  var isnan = require( '@stdlib/assert-is-nan' );
  var hasOwnProp = require( '@stdlib/assert-has-own-property' );
  
  
  // MAIN //
  
  /**
  * Validates function options.
  *
  * @private
  * @param {Object} opts - destination for validated options
  * @param {Options} options - function options
  * @param {number} [options.alpha] - significance level
  * @param {string} [options.alternative] - alternative hypothesis (`two-sided`, `less` or `greater`)
  * @param {number} [options.difference] - difference in means under H0
  * @param {string} [options.variance] - whether variances are `equal` or `unequal` under H0
  * @returns {(null|Error)} null or an error
  */
  function validate( opts, options ) {
  	if ( !isObject( options ) ) {
  		return new TypeError( 'invalid argument. Options argument must be an object. Value: `' + options + '`.' );
  	}
  	if ( hasOwnProp( options, 'alpha' ) ) {
  		opts.alpha = options.alpha;
  		if ( !isNumber( opts.alpha ) || isnan( opts.alpha ) ) {
  			return new TypeError( 'invalid option. `alpha` option must be a number primitive. Option: `' + opts.alpha + '`.' );
  		}
  	}
  	if ( hasOwnProp( options, 'alternative' ) ) {
  		opts.alternative = options.alternative;
  		if ( !isString( opts.alternative ) ) {
  			return new TypeError( 'invalid option. `alternative` option must be a string primitive. Option: `' + opts.alternative + '`.' );
  		}
  	}
  	if ( hasOwnProp( options, 'difference' ) ) {
  		opts.difference = options.difference;
  		if ( !isNumber( opts.difference ) || isnan( opts.difference ) ) {
  			return new TypeError( 'invalid option. `difference` option must be a number primitive. Option: `' + opts.difference + '`.' );
  		}
  	}
  	if ( hasOwnProp( options, 'variance' ) ) {
  		opts.variance = options.variance;
  		if ( !isString( opts.variance ) ) {
  			return new TypeError( 'invalid option. `variance` option must be a string primitive. Option: `' + opts.variance + '`.' );
  		}
  	}
  	return null;
  }
  
  
  // EXPORTS //
  
  module.exports = validate;
  