Saturday, July 31, 2010

Creating Perfect Graphs with Minimum and Maximum Slope for IB Physics IA's

Update: The New IB Physics Graphing Template for the 2016+ Syllabus is out! Follow this link to find out more!

All the links below are now OUT OF DATE!

Download the IB Physics Graph Template

Are you a Teacher? See my Guide to Teachers: Creating Perfect IB Physics Graphs.

I've been working on an Excel Template that will allow you to easily create ideal graphs for IB Physics IA's. Some of the features I'm trying to incorporate are:

1) Automatically draw the correct error bars based on the uncertainty of the measurement
2) Automatically draw the maximum and minimum slope based on the error bars
3) Fill in the graphs on-the-fly so you can see how the data is developing as you take measurements.

The template I'm building requires Microsoft Excel

Graphing Template for IB Courses with Max and Min Slopes

This template can be purchased for $2.00 USD using the Google Checkout Gadget below. Complete the purchase and you will be directed to a download link for the template. The IB Graph template is now free! Download here.

27 comments:

  1. Awesome! This made things a lot easier.

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  2. I'm glad you like it! If you have any problems, or ideas for features, let me know. I'm eager to make improvements :)

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  3. Well there something weird about it. The trendline sometimes has a higher slope than the max slope trendline. And when I go to trendline options and mark the box that gives the trendline equation, the result is different from the one that the template shows.

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    1. If your first or last data point is an outlier, that can make your slopes weird. The best fit line considers all the data points, but the max and min trendlines only consider the first and last. If either the first or last data point is way off, it has a much bigger effect on the max and min slopes than on the best fit line. You can tell that there is an outlier if the max and min trendlines don't pass through one or more of the data points.

      As for trendlines on the graph not matching the trendlines reported, are we talking about a significant difference, or just a tiny amount? I had to fudge some of the numbers a little because Excel doesn't like to graph vertical lines. If there's a significant difference, I would really like to see what's going on. Would you be able to post a screen grab of the document, or email me your document?

      EDIT: Sorry to come back to this question after so much time, but one of my students found the error you were experiencing. There was a difference between how I was calculating trendlines and how Excel was doing the same task. The problem has been fixed for a while now so I don't think anyone else should be experience this issue. Thank you again for your feedback, El @normal

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    1. What do they saaaaaaaaay??? https://www.youtube.com/watch?v=GdvD4Fhc_K8

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  5. Thank you very much, worked fine for me. I'm not too concerned about the trendlines personally, I just needed something that would graph a best fit line and show error bars for an IA. Had to do some digging to find this but it was worth it! Cheers!

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    Replies
    1. Glad you like it, Armin, and I'm happy you were able to get it to do what you want.

      For anyone else reading these posts you can remove the trendline by right clicking on it and selecting delete. You can also add different (ie, non-linear) trendlines by right clicking on the data and selecting add trendline. FYI this is the same way that trendlines work in any normal Excel Scatterplot.

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  6. Does this template work effectively if my data has a negative gradient but is still linear?

    This is the best thing ever for IB Physics, it's going to save me hours of fiddling around with excel ! Thank you so much!

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    1. Also, how do I find the average of the maximum and minimum slope equations?
      By hand I would find each gradient and then average them, and do the same with the y-intercept, is this how I would do it using this template too?

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  7. Hi Rhiannon!

    Negative gradients shouldn't be a problem. Just enter your data normally and the template should figure it out.

    As for the average of the max and min lines, personally I would just use the best fit line for whatever purpose you were thinking of using the average. The graph on the left hand side has the best fit line as calculated by excel's linear regression method.

    However, if you really want the average of the max and min lines, on the right hand graph you can read the slopes from the equations for the two lines. The slope term is the constant in front of the 'x'. You can also average the y-intercepts. That's the term after the 'x'. Just average those two and you should have the 'typical line' you're looking for.

    I'm glad to hear you find the template useful :)

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  10. My slope for the trendline is 0.0128 while the slope of the max/min slope lines is 0.0115 and 0.0114 respectively. Why is my max slope less than the trendline slope?

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    1. Hi Rohan,

      The best fit line (trendline) considers all your data points while the max and min slope lines consider only your first and last points and their respective uncertainties. Because of this if your first or last data point deviate too much from the rest of your data it can throw off the max and min slope lines.

      In your case, your uncertainties appear to be _very_ small because your max and min slope lines differ by only about 1%. I would guess that either you are entering uncertainties that are smaller than they should really be or you have outliers in your data (probably in the first or last data point).

      If you want to post your data I can have a closer look.

      Cheers.

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  11. Very interesting article!!
    I'd like to comment that MYP and IB (HL,SL,Math Studies) students maybe find helpful the IB math forum at IB maths 4u
    Thanks!

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  12. I just found this template, but I've already finished my graph and don't want to redo it. I'm having trouble getting the top and bottom error line caps to be easily visible when the y values ascend by 10s. I've already reduced the size of the data points, but the error line caps are still touching the data points. Any ideas?

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    1. Hi IB geek,

      It's not actually very hard to transfer your data into the template. Just copy and paste.

      If you want to do it your own way you can try removing the data points all together. If you have cross-hairs for your error bars, diamond shapes at the location of the data are not necessary. If that doesn't work, it may be that the error bars are just too small to be seen on the graph. You can add a foot-note in your report saying that the vertical error bars don't show up at the scale you're using. You can state what they are, as in, +/- 0.01 units.

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  13. Thank you for posting and creating this time-saving tool!

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  14. does not let me add 0.001 as uncertainty

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    1. Did the cell turn into hashes? Like #########? That's just Excel's way of telling you that what you typed doesn't fit in the cell. Expand the size of the column and you'll see the number as you typed it. Incidentally this doesn't effect the calculations, so the sheet should still work in any case.

      Let me know if that doesn't solve the problem.

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  15. Hey Mr Kann.

    I am so appreciate of this template really a life saver.

    However my IB teacher likes the graph to be in template "10" in chart type for the scatter graph however when i change the type all the data and trendlines disappear on the graph.

    Is it possible you could make an edited version with the chart type 10 instead? I would be happy to pay the $2.00

    Or if theres a easier solution please let me know. Thanks.

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    1. Hi junayd,

      Here's a link to the latest version (still in development). It should allow you to change the chart style (template). https://drive.google.com/file/d/0B-1eAQYKZo_5elhwaHc1dElUSUk/view?usp=sharing

      As a side note, as far as I know the IB Moderators don't care what chart style you use as long as it has (for a linear trend):
      axis titles
      chart name
      Error Bars
      trend line
      max and min slopes
      and the equations for the trend line and max and min slopes.

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