Week 11
Combinatorics

Business

The start of the week email.

⦿ Monday. Distributions of possible outcomes

Quincunx? Screencast 4:39
The ubiquitous bell curve/Gaussian distributon/normal curve (when you're ubiquitous you get named multiple times!) can arise from the sum of many individual random events. You can play with the Quincunx simulation yourself, or watch a video of an actual physical quincunx.
Quincunx! Pencast 16:14| PDF
Calculating Quincunx outcomes manually using Pascal's Triangle, and formulaically using combinations.
Back to coin flipping, and probability Pencast 13:32| PDF
Calculating probabilities of many, many tree paths, e.g. the probability of getting 7 heads in 10 tosses of a coin. This turns out to be a useful model for many, many phenomena.
Bernoulli trials and binomial distributions Pencast 10:16| PDF
If the Quincunx and coin flipping are the same, then of course mathematicians formalized and named their commonalities.

Exercises

If you're comfortable with the topics above you're ready to work on:

Supplementary resources:

The Math is Fun folks who provide the simulator have a good discussion of the Quincunx.

In College Mathematics for Everyday life by Inigo, Jameson, Kozak, Lanzetta, and Sonier
§4.3 covers the binomial distribution.

⦿ Wednesday. Case study: Mark-recapture

Mark and recapture Pencast 21:36| PDF
We can rarely go and count all the individuals in an animal population. Instead we have to take a sample and infer the population from the sample. Mark-recapture is a common way of doing this.

Exercises

If you're comfortable with the topics above you're ready to work on:

Supplementary resources:

I used the simplest possible mark-recapture model and formula here. Given its centrality to wildlife population management extensive work has been done on mark-recapture strategies and modelling. If you want to know more about Mark-Recapture techniques Chapter 2 Estimating Abundance and Density: Mark-Recapture Techniques in Ecological Methodology 3ed by C.J. Krebs is one well-written resource that is available online.

⦿ Friday: Graph Theory

What graph theory is: Introduction and background

Introduction to Graph Theory Video 4:56
The graphs of Graph Theory aren't like the ones you are used to, though I have drawn some from time to time. This video also goes over the jargon and nomenclature we use to describe and refer to graphs.
The Birth of Graph Theory Video 6:58
Graph Theory has an interesting origin story. Watch this if you're curious.
General Applications of Graph Theory Video 11:25
This narrated slide show describes some of the many applications of graph theory.
Applications of Graph Theory in the Life Sciences Video 11:31
This narrated slide show describes two applications of graph theory in the life sciences: Trophic webs, and Landscape connectivity.

Spanning Trees

Spanning trees PDF 1 page
Hand drawn notes explaining what spanning trees are. Because before we try to find minimal spanning trees, we need to know what they are.

Minimal Spanning Tree On-the-graph

MST example done on-the-graph Pencast video 4:35 | PDF
The MST algorithm is simple enough you might be able to learn it just by watching me do these two examples. But if not there are the detailed notes below to refer to.
Minimal Spanning Tree Algorithm: On-the-graph PDF 4 pages
Detailed notes on how to find the minimal spanning tree of a weighted graph.

Shortest Route Algorithm On-the-graph

Shortest Route example done on-the-graph Pencast video 9:44 | PDF
The shortest route algorithm involves some fussy bookeeping. You might want to skim the notes below before watching the example in this video.
Shortest Route Algorithm: On-the-graph PDF 3 pages
Detailed notes on how to find the shortest route from one node to another in a weighted graph.

Exercises

If you're comfortable with the topics above you're ready to work on:

Supplementary resources:

§6.1-6.3 in Chapter 6 of College Mathematics for Everyday life by Inigo, Jameson, Kozak, Lanzetta, and Sonier.

Chapter 6: Graph Theory in Math in Society by David Lippman.

5: Graph Theory in Combinatorics and Graph Theory by David Guichard.

Assignment

Assignment 11 is posted. Due by 1 pm Wednesday April 8. Note that the problems are worth different numbers of marks. Use your time wisely.

Name the file you submit A11_firstname.pdf, e.g.

A11_Tim.pdf

If you have to submit multiple files, add a suffix number to each, e.g.

A11_Tim_1.pdf
A11_Tim_2.pdf