Posted in Humor, Statistics

Who increased the debt? – a lesson on graphs

Graphs display information in an organized and easy-to-read manner.They are visual representations of quantities and their relationships so they are not pictures. That graphs are pictures is a common misconception.  By end of fourth grade a pupil should be able create, understand and interpret at least the basics of three types of graphs, line, bar graphs as well as pie charts.Fourth graders should learn the skills necessary to understand the importance, as well as the use of each graph. They should understand that a line graph is used to express change over a period of time, a bar graph is used to express the quantity of different items, and a pie chart is great for representing the quantity of an item out of one hundred percent. When the learners have understood each use they will be able to fully apply that knowledge into recognizing the importance of graphs in their lives especially in their political life:-)

Here’s a graph I found in my Facebook homepage. It’s an example of political bar graph, if there is such a type:-). What I love about this bar graph are the pictures they put on top. It helps one remember what these guys have been up to.

Interpreting graphs is a skill expected of a fourth grader but this post is not intended for them but for those who were once fourth graders.

Political Bar Graph

Suggested questions for discussion:

  1. What do the red and blue bars represent?
  2. If a red bar will be next to the rightmost bar now, will it be longer or shorter than the blue bar? Estimate and explain your assumptions?
  3. To what can you attribute the sharp decrease from President Reagan to G.H. W Bush?
  4. What other questions can you asked based on this graph?

I hope you will have a “fruitful” discussion. Here’s one discussion in my Facebook page:

Except for the math part, this post should not be taken seriously and the graph should certainly not find their way to the classroom.  For the history of that graph read: Nancy Pelosi’s questionable chart and Chart goes viral.

 

Posted in Humor

Facebook is CIA’s #1 online surveillance program – Humor

Facebook’s Mark Zuckerberg is now CIA’s # 1 agent.  And the government wants you to use Facebook. You are more trackable and traceable there than via your Twitter or Google+ accounts. View the flash report below from The Onions News Network (ONN).

Of course the CIA will not find fault with you liking Math for Teaching’s Facebook page. It’s a plus in your resume’. So go, like it in FB. If you don’t want to get traced, follow this blog in Google+, Twitter or subscribe by email. Thanks.

Posted in Math investigations, Teaching mathematics

What is cognitive conflict approach to teaching?

According to Piaget, knowledge is constructed when a learner encounters input from the environment and incorporates the new experiences to his/her existing schemes and mental structures (assimilation). When this new assimilated information conflicts with previously formed mental structures, the result is called disequilibrium – a cognitive conflict. This state of disequilibrium motivates the learner to seek equilibrium. The cognitive conflict approach to teaching is based on this assumption – that learners will seek this equilibrium.

Cognitive conflict approach to teaching exposes students in  situations where some of their existing understandings about an idea or a topic no longer hold. A famous example on this is the Chords and Regions activity:

Find a way of predicting the maximum number of regions created by chords connecting n points.

This activity is usually used to challenge students thinking that patterns observed will always hold true and that patterns can be used as proof. The pattern observed will not hold true for n > 5. You can read the result of this activity in this paper Chords and Regions.

The assumption that learners will seek equilibrium when they are put in a situation of disequilibrium, when they experience cogntive conflict isn’t often the case. In fact, a common challenge faced by the cognitive conflict approach is that students often possess ‘contradictory understandings’ (from a mathematical point of view) but they don’t feel the need to address the inconsistencies in their understandings. This is the reason why it is very hard to correct a misconception. Also, students often do not see the importance (or necessity) to engage in a process of modifying their understandings to resolve the contradictions and they tend to treat the contradictions as exceptions (Stylianides & Stylianides, ICME-11). In the above activity for example, instead of being challenged, students can just accept the fact that the pattern stops after n=5 and not try to think of a more general rule to cover all cases. It is also possible that students can just say Next time I’ll try up to 10 cases before generalizing. This is now the challenge to the teacher. As a teaching approach, the use of cognitive conflict has a lot of potential but it needs more than simply using the appropriate task to create the conflict. Our students can be very resilient.

Mary Pardoe via LinkedIn discussion suggests that a strategy that encourages students to confront, rather than avoid, a cognitive conflict is to challenge small groups of students to reach a group conclusion (about the situation) with which everyone in the group agrees. Students who individually might respond differently to the ‘conflict’ will usually then try to persuade each other that their own points of view are correct, and so they are motivated to explain and discuss their thinking. Sample teaching using this approach is described in Using cognitive conflict to teach solving inequalities.

Common misconceptions are also rich sources of tasks for creating cognitive conflict. Click the link Mistakes and Misconceptions and Top 10 Errors in Algebra for sample of tasks.

You may want to check the book below to get more ideas on teaching mathematics.

Constructing Knowledge for Teaching Secondary Mathematics: Tasks to enhance prospective and practicing teacher learning (Mathematics Teacher Education)

 

Posted in Algebra, High school mathematics

Free online calculator for problem solving and math investigation needs

Meta-Calculator is  a free online calculator that should serve the needs of almost any high school student/college student for problem solving and math investigations tasks. It would also be useful for anyone who needs to analyze statistical data, do lots of calculations , graph equations or create images of equations—you can just hop on the internet browse to the webpage and download the graph!

Meta-Calculator is a multi purpose calculator that works both in your browser via the Flash Plugin and on your iphone/ ipad as an app–so pretty much every modern computer/phone  out there can use it.  It is really four calculators in one—a scientific one,  graphing calc, statistics calculator and a matrices/vector calculator.  Let’s look at each one in detail.

The Graphing Calculator

Meta Calc can graph up to 7 equations or inequalities,  find their intersections,  produce a table a values or trace a point along any equation. You can also zoom in/zoom out , set the x-scale or y-scale, x-min/max, y-min/max, pan around the graph with your mouse.  A distinctive feature is the ability to save any of your graphs as images to your computer ( .png files). Just hit the ‘save graph’ button, and you will download the graph. This is a feature that any student or teacher could appreciate—the next time you need a graph for a presentation or a worksheet for your math lesson, just type in the equation and hit ‘save graph.’  I actually know some teachers that have used this very feature to introduce slope. One teacher, for instance, graphed 7 equations, slightly changing the slope for each one, and then let her students explore the relationship between the slope of a line and its graph.

The Scientific Calculator

The scientific calculator provides a really intuitive user experience.  It has all of the basic functions and buttons you’d expect including sin, cos, sin-1, cosh, log and more. Plus it has some more advanced features including a button to calculate   least common multiples, permutations, combinations and—possibly most powerful of all—a linear equations solver that lets you input up to 6 equations with either two or three variables and the solver will calculate the solutions.

The Matrix Calculator

The matrices/vector calculator has a wide range of functions. You can calculate a matrix’s determinant, or its inverse. Also, you can add, subtract, multiply and transpose matrices. The same functions are available for vectors.

The Statistics Calculator

Last but definitely not least is the statistics calculator. This has the fundamentals that you’d expect: calculating quartiles, mean, median, mode as well as correlation coefficient and various types of regressions (linear, quadratic, exponential, cubic , Power, Logarithmic, Natural Logarithmic).    You can then plot the data to the graphing calculator! A stand-out features is the ability to compute  Student t-tests: either 1 or 2-Tailed T-Tests (paired and unpaired). I was unable to find any calculators online that let you enter raw data and calculate T-tests so this is quite a rare online find.

The calculator can be found here : http://www.meta-calculator.com/online/.