text: const stddev = require('./stddev');
  const variance = require('./variance');
  const coevar = require('./coevar');
   
  class Dispersion {
      constructor (numbers) {
          this.numbers = numbers || [];
      }
  
      variance() {
          return variance(this.numbers);
      }
  
      stddev() {
          return stddev(this.numbers);
      }
  
      coevar() {
          return coevar(this.numbers);
      }
  }
  
  module.exports = Dispersion;