1. Intro CS – Probability and Random Numbers
Lesson Plan 6a

2. Goals
Students can explain random numbers and how computers can generate them
Students can generate random numbers
Students can use the computer to simulate random number experiments to observe probability statistics
Students can predict probability statistics for a given problem
Students can express probability as ratios, decimals, and percentages
Students can write code to generate probability statistics as ratios, decimals, and percentages

3. Objectives
Students are introduced to random number generation by computers and how they can be used to simulate chance
Students are given real probability problems to code and solve
Results are demonstrated through predications, demos of running code, and displayed results

4. Pre Requisites
Knowledge of IF blocks, Loops (to simulate mutiple trials), variables (to capture results)
Basic Understanding of BYOB

5. Materials Slides with examples (or present on whiteboard)
PCs with Chrome browser to access Snap web site

6. Lesson Description
Students learn about random number generation in computers, and how it can be used simulate probability experiments
Students practice and extend examples
Students solve probability problems using code and the computer
Students analyze their and others’ solutions, and collaborate towards shared solutions

7. Lesson Procedure
Warm-up: Define/research what probability is, with an example. Research an example of how random numbers are used with computers to simulate chance
Quick review of IF block, Variables, and Loops
Introduce PICK RANDOM through student investigation and observation of sample work
Give exercises for in class practice
Walk the room answering questions, looking over the shoulder, asking questions, etc.
Check off solutions for completeness and accuracy
Review

8. Closure/Conclusion Summary
Random numbers are a powerful way to simulate real world problems and introduce random behaviors into normally predictable code
Future thinking: Discuss Monte Carlo simulations as they relate to Finance, Airplane Boarding Optimization, Sporting Event Results
Ask questions on what is confusing or needs more time/practice

9. Random Numbers
Lesson 5

10. Warm-up Research/define probability, with a real-life example
Research another example of how computers are used to simulate chance

11. Review: IF blocks What are IF Blocks?
IF blocks are used to help make decisions and branch your code.
When the IF Block statement is true, whatever is contained inside the decision block is done
Other blocks that use logic: IF/ELSE, Repeat Until, Wait Until
Can anyone tell me what they think an IF block will do?
What do you think this sequence will do?
Note: Here a double inquiry about “if on edge” happens. The block used can be applied even without the decision-block. But for gaining understanding of the concept decision this way works better.

12. Review: Variables Variables are places we can store results/values
Variables can be changed any time
Variables can be incremented by one to count things

13. Review: Loops Used to repeat things a few to many, many times
Can repeat:
Forever (FOREVER block)
A specific number of times (REPEAT 10 block)
Until a test is True (REPEAT UNTIL <test> block)

14. Generating Random Numbers
Usually, computers are very predictable
3+5 will also equal 8 for a computer
Spell checking, etc.
Sometimes we want computers to simulate life by being less predictable
We can use Random Numbers to:
Simulate chance (rolling dice, unpredictable events, etc.)
Track results in variables
Run thousands/millions of simulations very fast
We use the Pick Random block (on the green tab)

15. Investigation Pair up. If you get stuck, ask another pair.
Simulate the following by having a sprite Say:
the result of rolling one six-sided die
the result of rolling two, three, four, or five six-sided dice
the result of rolling one ten-sided die
the result of picking a random card from a deck
sprite must say "Ace of Clubs", "6 of Hearts", etc.
Hint: use Join block on green tab to put words/numbers together, and IF blocks

16. When to use Pick random When you want to simulate chance:
50/50
99/1
When you want to wait a random amount of time
Wait (pick random 6 to 10)
When you want to pick a random thing from a list of things
Picking a word in Hangman (future project in class)
When you want to make game behavior unpredictable
Sometimes go left, sometimes right, etc.

17. Coding problem Write the following programs:
Computer rolls 2 dice, calculate the probability of each roll (2-12)
Use the computer to roll 5 dice to play Yahtzee
Roll dice, pick all/some/none to keep, repeat 3 times
Mark (on paper, or write code), to track which scores to take after 3 roles
Repeat until you can't play, or all categories filled

18. Review
You’ve just learned the basics of random numbers and using computers to measure probability
Simulate chance
Experiment to calculate results
Future thinking: Monte Carlo calculations
Finance: predict retirement outcomes
Sports: predict team scores
Airplane boarding optimization: predict and test models