toFixedメソッドが適用されない

下記コードのupdateTime関数内の変数「accuration」において、toFixedメソッドを通しているのですが、適用されなかった為、原因が分からずご質問させて頂きました。

'use strict';
{

  let words =  ['blue','apple','sky','middle','set'];
  let word;
  let isPlaying = false;
  let loc = 0;
  let target;

  let letter_count = 0;
  let miss_count = 0;
  let miss_label;
  let letter_label;
  let timeLimit;
  timeLimit = 3 * 1000;
  let start_time;
  let time_label = document.getElementById('time_left');
  let accuracy

  window.addEventListener('click',() => {
    if(isPlaying == true){
      return;
    }

    function updateTime(){

      let time_left = start_time + timeLimit - Date.now();
      time_label.textContent = (time_left / 1000) .toFixed(2);

      const time_out_id = setTimeout(() => {
        updateTime();
      },10);

      if(time_left < 0){
        isPlaying = false;
        clearTimeout(time_out_id);

        if(letter_count == 0 && miss_count == 0){
            accuracy = 0;
        }else if(miss_count == 0){
            accuracy = 100
          }else if(letter_count == 0){
            accuracy = 0;
          }else{
            accuracy = (miss_count / letter_count) * 100;
            accuracy.toFixed(2);
            console.log(accuracy);
          }

        console.log(miss_count);
        console.log(letter_count);
        window.alert(letter_count + 'letters,' + miss_count + 'misses, ' + accuracy + '%accuracy!');
      }
    }

    isPlaying = true;


    letter_label = document.getElementById('Letter_label'); 
    miss_label = document.getElementById('Letter_miss_label');
    target = document.getElementById('top_word');
    word = words[Math.floor(Math.random() * words.length)];
    target.textContent = word;
    start_time = Date.now();
    updateTime();

  });

  window.addEventListener('keyup', e => {
    if(isPlaying === true){
      let placeholder = '';



      if(e.key == word[loc]){
        loc++;
        letter_count += 1;
        console.log(letter_count);
        letter_label.textContent = letter_count;

        for(let i = 0; i < loc; i++){

          placeholder += '_';
        }


        console.log(word.substring(loc));
        console.log(placeholder);
        target.textContent = placeholder + word.substring(loc);


      }else{
        miss_count++;
        miss_label.textContent = miss_count;
      }

      if(loc == word.length){
        word = words[Math.floor(Math.random() * words.length)];
        target.textContent =  word;
        loc = 0;
      }

    }

  });

}

updateTimeメソッド内のaccurationが「33.33333」であったとしても、toFixedメソッドを通した場合でも、変わらず、console.log(accuracy);の出力結果は変わらず、「33.33333」になってしまいます。
原因究明の為、ご助言頂けましたら幸いです。