{"id":546,"date":"2025-11-26T03:44:12","date_gmt":"2025-11-26T03:44:12","guid":{"rendered":"https:\/\/learndeeplytw.com\/?p=546"},"modified":"2025-11-26T03:44:17","modified_gmt":"2025-11-26T03:44:17","slug":"decision-tree","status":"publish","type":"post","link":"https:\/\/learndeeplytw.com\/en\/decision-tree\/","title":{"rendered":"Who is the Mind-Reading Detective? Learning How Computers Make Decisions"},"content":{"rendered":"<p class=\" translation-block\">We often assume that \"information\" refers to words written in a book\u2014the more words, the more information. But computer scientist Claude Shannon taught us that <strong>information is actually \"Surprise.\" <\/strong>If I tell you something you already know (e.g., \"The sun rises in the east\"), the amount of information in that sentence is effectively zero.<\/p>\n\n\n\n<p class=\"\">To teach children this abstract concept, and how computers use it to compress data or make Decisions, we don't need advanced calculus. We just need a classic game: \"20 Questions.\"<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Phase 1: Experiencing Frustration (The \"Bad\" Strategy)<\/h3>\n\n\n\n<p class=\"\">Before teaching \"Binary Search,\" let the child experience the pain of having \"No Strategy.\"<\/p>\n\n\n\n<p class=\"\"><strong>1. Game Setup:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\">The teacher thinks of a number between 1 and 100 (let's say 86).<\/li>\n\n\n\n<li class=\"\">The child guesses, but can only ask \"Yes\/No\" questions.<\/li>\n<\/ul>\n\n\n\n<p class=\"\"><strong>2. Observation &amp; Listening (Crucial Moment):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\">Many children will intuitively ask: \"Is it 1?\" \"Is it 2?\"<\/li>\n\n\n\n<li class=\" translation-block\">\u274c Don't interrupt. Patiently answer \"No,\" \"No.\"<\/li>\n\n\n\n<li class=\"\">Wait until the 5th or 10th question when they start getting impatient. This is the perfect teachable moment.<\/li>\n<\/ul>\n\n\n\n<p class=\"\"><strong>3. Constructive Inquiry:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"Do you feel that guessing one by one is tiring? If you're unlucky and the answer is 99, how many times do you have to guess?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>\"99 times...\"<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>\"What if we turned this into a contest where<strong>the person who asks the fewest questions wins?<\/strong>Or, imagine every question costs you $10. Would you want to change your strategy?\"<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Phase 2: Discovering Binary Search<\/h3>\n\n\n\n<p class=\"\">Guide the child to think about how to \"eliminate\" the maximum number of wrong answers.<\/p>\n\n\n\n<p class=\"\"><strong>\u2705 Effective Scaffolding Dialogue:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"Is there a kind of question that, by asking just once, allows you to throw half of the numbers into the trash bin\u2014like slicing a watermelon in half?\"<\/li>\n\n\n\n<li class=\"\"><em>(Give them time to think or draw diagrams.)<\/em><\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>\"Is it bigger than 50?\"<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>: \"Brilliant! If I say 'Yes,' what happens to the pile of numbers from 1 to 50?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>: \"We don't need to guess them anymore!\"<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>: \"Exactly! You just spent $10 (one question) to filter out 50 numbers. Isn't that much better value than asking 'Is it 1?'\"<\/li>\n<\/ul>\n\n\n\n<p class=\" translation-block\"><strong>Activity Implementation:<\/strong><br>\nLet the child play the number guessing game again using this new strategy (Greater\/Less than). Guide them to discover that no matter what the number is (1-100), they can always find it within <strong>7<\/strong> guesses<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Phase 3: Drawing the Decision Tree<\/h3>\n\n\n\n<h5 class=\"wp-block-heading\">Step 1: Visualization (Before handing out the worksheet)<\/h5>\n\n\n\n<p class=\"\">Before showing the diagram full of arrows, keep the momentum going.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"When we played just now, what was happening inside your brain? Can you draw your 'Thinking Path' for others to see? Let's try a smaller range, 0 to 7. If your first question is 'Is it \u22654 ?', where do you go next?\"<\/li>\n\n\n\n<li class=\"\"><em>(Let them scribble on blank paper. The point is to make them realize that thinking involves branching.)<\/em><\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">Step 2: Decoding the Map (Exploring the Worksheet)<\/h5>\n\n\n\n<p class=\"\">Now, bring out the diagram. Tell them: \"This is a 'Thinking Map' drawn by computer scientists. Let's see if it matches yours.\"<\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"458\" src=\"https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-1024x458.webp\" alt=\"\" class=\"wp-image-551\" srcset=\"https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-1024x458.webp 1024w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-300x134.webp 300w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-768x344.webp 768w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-18x8.webp 18w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees.webp 1086w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n\n\n\n<p class=\"\"><strong>1. Task: Path Tracing<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Scenario<\/strong>\"We are looking for the number&nbsp;<strong>5<\/strong>. Put your finger on the start node at the top. Let's walk the path.\"\n<ul class=\"wp-block-list\">\n<li class=\" translation-block\">First Check: x\u22654? Is 5 greater than or equal to 4? \u2192 Child: \"Yes!\" \u2192 Teacher: \"Okay, let's go down the 'Yes' path.\"<\/li>\n\n\n\n<li class=\" translation-block\">Second Check: Now at x\u22656?. Is 5 greater than or equal to 6? \u2192 Child: \"No!\" \u2192 Teacher: \"Okay, let's take the 'No' path.\"<\/li>\n\n\n\n<li class=\" translation-block\">Third Check: x\u22655? Is 5 greater than or equal to 5? \u2192 Child: \"Yes!\" \u2192 Teacher: \"Go 'Yes.' Look! Did we find 5?\"<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p class=\"\"><strong>2. The Constructivist Hook<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"How many decisions did you have to make to find 5?\"<\/li>\n\n\n\n<li class=\"\"><em>(Guide them to notice that finding any number in this range requires exactly 3 decisions).<\/em><\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">Step 3: The Secret of Binary (The \"Aha!\" Moment)<\/h5>\n\n\n\n<p class=\" translation-block\">This is the most brilliant part of the map: <strong>The Path IS the Code.<\/strong><\/p>\n\n\n\n<p class=\"\"><strong>1. Observing the Rule:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"What if 'No = 0' and 'Yes = 1'? Let's look back at the path we took to find 5.\"<\/li>\n\n\n\n<li class=\"\"><strong>Backtracking<\/strong>Guiding Reflection:\n<ol class=\"wp-block-list\">\n<li class=\"\">Step 1: Yes (Write down 1)<\/li>\n\n\n\n<li class=\"\">Step 2: No (Write down 0)<\/li>\n\n\n\n<li class=\"\">Step 3: Yes (Write down 1)<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>:\"String these three numbers together. What do you get?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>\uff1a\u300c1&#8230; 0&#8230; 1\uff1f\u300d<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>: \"Do you remember the binary cards? What is the binary code for 5?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>(Surprised) : \"It's also 101!\"<\/li>\n<\/ul>\n\n\n\n<p class=\"\"><strong>2. Verification &amp; Consolidation:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"Is that a coincidence? I don't believe it. Pick another number (e.g., 3), walk the map, write down the path as 0s and 1s, and check if it matches its binary code.\"<\/li>\n\n\n\n<li class=\" translation-block\">(Let them verify it themselves. When they see every number matches, they grasp the essence: <strong>Binary is simply a record of a series of Yes\/No decisions.)<\/strong><\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-28f84493 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\">\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"454\" src=\"https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-1024x454.jpeg\" alt=\"\" class=\"wp-image-554\" srcset=\"https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-1024x454.jpeg 1024w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-300x133.jpeg 300w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-768x340.jpeg 768w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-1536x681.jpeg 1536w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1-18x8.jpeg 18w, https:\/\/learndeeplytw.com\/wp-content\/uploads\/2025\/11\/Decision-Trees-with-01-1.jpeg 1552w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n<\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">Phase 4: What is Information? (Surprise = Information)<\/h3>\n\n\n\n<p class=\"\">Understanding Shannon's Information Theory via the \"Nonsense Test.\"<\/p>\n\n\n\n<p class=\"\"><strong>Scenario Dialogue:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"Let's play a game to see who can say the most 'boring' sentence (least information).\"\n<ul class=\"wp-block-list\">\n<li class=\" translation-block\">Example A: Mom says, \"I walked on my feet to work today.\"<\/li>\n\n\n\n<li class=\" translation-block\">Example B: Mom says, \"I took a UFO to work today.\"<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>: \"Which sentence makes your jaw drop?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>: \"The UFO one!\"<\/li>\n\n\n\n<li class=\" translation-block\"><strong>Teacher<\/strong>: \"Right. You already knew the first one, so it has zero new information for you. The second one is completely unexpected, so the amount of information is huge.\"<\/li>\n<\/ul>\n\n\n\n<p class=\"\"><strong>Connecting back to Number Guessing:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\"\"><strong>Teacher<\/strong>: \"Back to the game. If the number is between 1 and 100, it's hard to guess, so the answer carries a lot of information (you need 7 questions).\"<\/li>\n\n\n\n<li class=\"\"><strong>Teacher<\/strong>: \"But if I say the number is between 1 and 2. How many questions do you need?\"<\/li>\n\n\n\n<li class=\"\"><strong>Child<\/strong>: \"Just one!\"<\/li>\n\n\n\n<li class=\" translation-block\"><strong>Teacher<\/strong>: \"Because it's not surprising and easy to guess, the information amount is small. This is Shannon's secret: <strong>The harder it is to guess, the more information it holds, and the more space (bits) the computer needs to store it.<\/strong>\"<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">Phase 5: Application &amp; Summary<\/h3>\n\n\n\n<p class=\"\">Why does this matter?<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li class=\" translation-block\"><strong>Teacher<\/strong>: \"Do you know how 'Autocorrect' on your phone works? When you type 'Good,' the phone has a Decision Tree in its mind. It guesses there is a 90% chance the next word is 'Morning,' and only a 1% chance it is 'Pizza.' So it puts 'Morning' on the easiest branch to reach. That is computers using Probability and Decision Trees to save you time.\"<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Teaching Observation Checklist<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td>Observation Point<\/td><td>Less Effective Reaction<\/td><td>More Effective Scaffolding<\/td><\/tr><tr><td><strong>When the child insists on linear guessing (1, 2, 3...)<\/strong><\/td><td>\"That's too slow. Use Binary Search.\" (Giving the Algorithm)<\/td><td>\"Do you want to try a question that can delete half the numbers at once?\"<\/td><\/tr><tr><td><strong>Explaining the Tree Diagram<\/strong><\/td><td>\"This is a Decision Tree. Memorize it.\"<\/td><td>\"Can you draw how your brain was thinking just now? If the answer is YES, which way do your thoughts go? What if it's NO?\"<\/td><\/tr><tr><td><strong>Explaining Information (Entropy)<\/strong><\/td><td>\"Information is Entropy. The formula is...\"<\/td><td>\"If I tell you 'The sun is hot,' how much is that sentence worth? If I tell you 'Tomorrow's lottery numbers,' how much is that worth? Why?\"<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">Summary<\/h3>\n\n\n\n<p class=\"\">Through this unit, children learn more than just \"guessing tricks.\" They learn:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li class=\" translation-block\"><strong>Algorithmic Efficiency<\/strong>: The massive difference between Linear Search (guessing one by one) vs. Binary Search (halving).<\/li>\n\n\n\n<li class=\" translation-block\"><strong>Data Structures<\/strong>: How to use a Tree to organize logic.<\/li>\n\n\n\n<li class=\" translation-block\"><strong>The Essence of Information<\/strong>: Information is a tool used to \"eliminate uncertainty.\"<\/li>\n<\/ol>\n\n\n\n<p class=\"\">Next time the child plays \"20 Questions,\" try praising them:\n\"Wow! That question was powerful. You just killed thousands of wrong answers in one shot. Your question had a huge amount of information!\"<\/p>\n\n\n\n<p class=\"\">Reference :<a href=\"https:\/\/classic.csunplugged.org\/documents\/activities\/information-theory\/Information-Theory-Chinese-Version.pdf\" target=\"_blank\" rel=\"noopener\">https:\/\/classic.csunplugged.org\/documents\/activities\/information-theory\/unplugged-05-information_theory.pdf<\/a><\/p>\n\n\n\n<div style=\"height:0px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<div style=\"height:100px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-core-columns-is-layout-28f84493 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\"><\/div>\n\n\n\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\"><\/div>\n<\/div>\n\n\n\n<p class=\"\"><\/p>","protected":false},"excerpt":{"rendered":"<p>\u6211\u5011\u5e38\u4ee5\u70ba\u300c\u8cc7\u8a0a\u300d\u5c31\u662f\u5beb\u5728\u66f8\u88e1\u7684\u5b57\u3002\u5b57\u8d8a\u591a\uff0c\u8cc7\u8a0a\u8d8a\u591a\u3002\u4f46\u96fb\u8166\u79d1\u5b78\u5bb6\u590f\u8fb2\u544a\u8a34\u6211\u5011\uff1a\u8cc7\u8a0a\u5176\u5be6\u662f\u300c\u9a5a\u559c\u300d\u3002\u5982\u679c\u6211\u544a\u8a34 [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":556,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","footnotes":""},"categories":[9,17],"tags":[38,13,26,36,37,24],"class_list":["post-546","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cs-unplugged","category-representing-information","tag-38","tag-13","tag-26","tag-36","tag-37","tag-24"],"blocksy_meta":[],"_links":{"self":[{"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/posts\/546","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/comments?post=546"}],"version-history":[{"count":7,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/posts\/546\/revisions"}],"predecessor-version":[{"id":564,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/posts\/546\/revisions\/564"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/media\/556"}],"wp:attachment":[{"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/media?parent=546"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/categories?post=546"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learndeeplytw.com\/en\/wp-json\/wp\/v2\/tags?post=546"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}