シャドーイング練習: Introduction to statistical prediction models - 動画で英語スピーキングを学ぶ

In this video I will give you a very short introduction to what statistical prediction is and what statistical prediction models are.

And my goal of this video is to try to you to understand what a large language model,

which is the technology underlying these AI chatbots,

what they do and why they sometimes hallucinate or give you incorrect answers.

So let's start with a more effective example.

This is Claude III, the smallest model,

and this is something that I encountered when I was preparing material for a doctoral level entrepreneurship course.

And I asked what is the contribution of Israel Kirchner in modern entrepreneurship, and then I asked Claude to explain or give me his biography.

And it starts well, most of this is correct.

So Israel Kirchner was born in 1930s, and then the biography ends that he passed away at 2021 at the age of 90.

Well, he is very much alive still.

So if you google his name, you can view that the dead guy is giving a talk on YouTube in 2023.

So now the question is, why does the large language model,

Claude in this case, give us this incorrect answer that the person who is alive was actually died a couple years ago.

To understand why we get incorrect answers from these tools, we need to understand a bit about what they do.

So let's talk about statistical prediction a bit.

So here's our some data, then we're going to fit a statistical prediction model to this data.

So we have sales, a fictional company how many units they sell and this is how much they advertise.

This might be something expensive equipment and this is your advertisement spending thousands, let's say that it's over a year.

And we can see that if the company doesn't advertise anything they sell about 150,

130 something that units and then there is this declining returns to advertisement.

So a little bit of advertisement gets you from 150 to 200, but then going beyond 200 is much more difficult.

So we have diminishing returns.

The simplest way to model this data statistically is to use a regression model.

And regression model happens to be the simplest statistical prediction model.

The idea of a regression model is that we try to explain this data with a line.

And we draw the line through the data.

How the line is defined is not important for this talk, but it's a line that describes the data.

And this line is defined by two parameters.

So these parameters define a model.

So we are saying that this beta 0 gives us what is the the value of the dependent variable,

the predicted variable, the sales when ad spending is zero,

and then beta 1 gives us how many units the sales increases for each thousands of dollars spend on advertisement.

In machine learning, you might also see that these are called weights and biases.

So the beta one is weight because it tells how much ad spending affects sales,

and then beta zero is called the bias because it tells what is the overall level of sales, even if we don't do any advertisement.

And how the recursion line here is calculated is that we take the bias 158,

we add weight times add spending, and then if we want to generate observations from this model, we add some error.

So the idea of error is that there's some variation in the actual values around the predicted line.

So this equation without error here gives you the recursion line, and if you want to simulate observations from this data then you would add error.

So we can use this line to simulate more data.

So if we have, if we know ad spending, then we can just plot more predicted sales values here.

This works fairly well as long as you predict within samples.

So if you predict something that is, you have data, so our predictions work fairly well between zero and fifty thousand.

We are predicting a bit more here than what we are observing.

Problems occur when we start to extrapolate.

So if we are asking this model to predict how much we would sell if we actually increased our sales spending,

our advertisement spending, to a million.

Here's the data.

So we can predict what the sales would look like if we advertised for a million dollars.

Now this model is not very trustworthy for this kind of predictions.

First of all, it doesn't consider that advertisement has diminishing returns.

So the first dollar is more valuable than the tenth dollar and so on.

Also there are probably other constraints that come into play.

So So just increasing your advertisement 100-fold will not increase your sales 100-fold.

There are other constraints.

So the real value might be somewhere closer to 200 or 500 units than 1,500 units.

So extrapolation generally is not good in statistical models.

At least this line of gross extrapolation.

So we need to understand now that we calibrate the model using data, in this case a regression model.

It gives us some parameters and that parameters, they give us an equation and we can use the equation to calculate predictions.

The predictions are closed with original data as long as the values that we predict with our closed-grid original data.

All right, now let's take a look at how this same idea works with text.

So this is our training data and we are going to specify a small language model

and we try to predict more text like this.

And the idea of modeling language is that instead of looking at what is the predicted sales are given advertisements.

We look at what is the predicted word given the previous word.

And this kind of model will be called biogram, but it's not super important to understand how it works.

But the general idea is that when we start to train this kind of a prediction model that works with language, we take a look at, for example, the word the.

And the is here, and the is followed by cat three times.

It's followed by dog once and mat once.

So we can say that when we see the word the, then 60% of the case we have cat as the next word, and 20% of the case we have dog,

20% case we have mat.

So that gives us kind of like these probabilities and we can start simulating new data from this model.

Then after cat we have sat, the and ran.

So all of these have 33% probability and so on.

So we can calculate the probabilities.

This is the word here on this on rows and then columns is the next word.

We can start using this model to generate data.

And this is what large language models do.

So we have an initial, let's call it prompt.

So this is what we would write to chat GPT, for example.

We just start with the.

And then what the model looks at, it looks that, okay, the word is the.

When we predict the next word, we have cat, 60% dog, and then 20% mat.

And it randomly picks one of these.

This has 60% probability 20% and 20% and it picks cat by random.

Then after cat we have either ran, sat and the with equal probabilities,

the model just picks randomly sat.

And after sat we always have on, so that is what the model predict,

and so on until it predicts away, which is the last word.

and this is how language models work.

So we have a word and then we predict what is the next word.

Then we take the predicted word and we predict the following word.

This is a pretty simple thing and this story doesn't really make sense.

The cat sat on the cat, sat on the mat, the cat sat on, the cat ran away.

But it looks somewhat similar to the original data.

We can make this a lot better if we start to look at broader context.

So instead of looking at just previous word, we could take a look at the two previous words or three previous words.

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We can increase the context length.

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So this small language model has context length of one word, and then we have 81 parameters because we have 81 probabilities.

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I just didn't include the zeros in this matrix.

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This is how ChatGPT works.

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So it looks what I have written this far, what is the likely next word.

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ChatGPT, Claude, Gemini, they all work with the same principle, they are just a lot bigger.

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So instead of 81 parameters like we have here, these models are in the hundreds of billions,

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probably the trillions of parameters and the context length is not one word, but it is something called a token,

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which is like a word part or a letter combination.

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And for example, Claude has 100,000 tokens.

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That's like multiple books that it looks at when it tries to predict the next word.

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Now we get to look at why did Claude predict incorrectly.

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And this is because of XAAAs.

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So the training data for Claude

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when it was trained using like most of the internet does not contain information about the death of Kirchner

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and it's natural because he is still alive.

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And here we have that the person died, was born in 1930,

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and the training data also contains lots of biographies of people born in 1930

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and most of those biographies end with explaining when the person passed.

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So the language model does not have information about the passing of Kirchner,

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but it has seen a general pattern that when the biography starts by telling that the person was born in 1930,

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then the likely ending for the biography is just that the person died somewhere in 2020s for example.

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So this is the basic idea of statistical prediction.

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You calibrate the data, calibrate a model based on data, and then you try to predict new observations.

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In large language models you predict the next word or the next word part.

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In recursive models you predict a value, for example.

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このレッスンの語彙とスピーキングのポイント

このC1レベルのスピーキングレッスンは、動画「Introduction to statistical prediction models」を教材にしています。繰り返し出てくる語は次のとおりです：model, word, predict, prediction, cat。この動画には、シャドーイング用の文が125文、単語が1690語あります。音声の長さは11:51です。話す速さは1分あたり約143語で安定しており、シャドーイングしやすいペースです。単語の86%は英語の頻出3,000語に含まれます。残りは練習の前に確認しておきましょう。

この動画の重要語彙

動画の中で特に難しい単語15語を、発音と意味つきで紹介します。

単語	発音	意味
predict 動詞	/pɹɪˈdɪkt/	予言する
prediction 名詞	/pɹɪˈdɪkʃən/	予言, 予測
advertisement 名詞	/ˈædvɚˌtaɪzmənt/	広告, ＣＭ
parameter 名詞	/pəˈɹæm.ə.tɚ/	媒介変数, パラメーター
biography 名詞	/baɪˈɑɡɹəfi/	伝記
probability 名詞	/ˌpɹɑ.bəˈbɪl.ə.ti/	確率
regression 名詞	/ɹiːˈɡɹɛʃ.ən/	回帰
calibrate 動詞	/ˈkæl.ɪ.bɹeɪ̯t/	調整する, 較正する
simulate 動詞	/ˈsɪm.jə.lət/	シミュレートする
advertise 動詞	/ˈædvɚˌtaɪ̯z/	広告する
calculate 動詞	/ˈkælkjʊleɪt/	計算する
incorrect 形容詞	/ˌɪn.kəˈɹɛkt/	間違った
equation 名詞	/ɪˈkweɪ.ʒən/	方程式
constraint 名詞	/kənˈstɹeɪnt/	束縛
extrapolation 名詞	/ɛkˌstɹæp.əˈleɪ.ʃən/	外挿

動画に出てくる句動詞

単語	意味
run away 動詞	逃げる, 逃走する

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	was born · is defined · are called
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	have sat · have written · has seen
関係詞節 who / which + 節 — 人や物について情報を加える	person who is · away, which is

注意したい発音

話し手はdoesn't, didn't, don'tなど、短縮形や弱形を6回使っています。聞こえたとおりの短い形で発音しましょう。

「th」の音: trustworthy /ˈtɹʌst.wɜː.ði/, tenth /tɛnθ/
「sh」と「zh」の音: prediction /pɹɪˈdɪkʃən/, regression /ɹiːˈɡɹɛʃ.ən/, equation /ɪˈkweɪ.ʒən/, diminish /dɪˈmɪnɪʃ/, extrapolation /ɛkˌstɹæp.əˈleɪ.ʃən/
長い単語（アクセントの位置に注意）: advertisement /ˈædvɚˌtaɪzmənt/, parameter /pəˈɹæm.ə.tɚ/, biography /baɪˈɑɡɹəfi/, probability /ˌpɹɑ.bəˈbɪl.ə.ti/, extrapolation /ɛkˌstɹæp.əˈleɪ.ʃən/

この動画での練習方法

まず声を出さずに動画を最後まで聞き、知らない単語をメモします。
通常の速度で一文ずつシャドーイングし、話し手のリズムに合うまで繰り返します。
自分の声を録音して元の音声と比べます。predict, prediction, advertisementなどの単語に特に注意しましょう。

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

シャドーイング練習: Introduction to statistical prediction models - 動画で英語スピーキングを学ぶ

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