The primary analysis I used for my fire ant analysis was an ANCOVA. Apparently, this is the standard method of teasing apart background effects for studies like mine where there is one treatment field and one field observed to account for seasonal variation. I found it a little frustrating because, in order to do an ANCOVA, you must first show that the response variable changes in response to the covariate and that there is a significant correlation between the covariate and independent variable. Since I did multiple ANCOVAs on different species of ants and some fit the model and some didn't, I was a bit nervous that I would have to go back to square one and find a new model to analyze the data. However, after some consultation, it turns out that as long as the model is appropriate for some of the other species and the species in question shows some trends towards at least one of the statistical tests for appropriateness of the ANCOVA, then it is ok to use the model. PHEW!
ANCOVA
Multiple players
Unstack the deck
Now deal
~from "The Tao of Statistics" by Dana K. Keller
Wednesday, May 9, 2007
Tuesday, May 1, 2007
My learning curve...
While working on my final project this evening, I had a realization. Not only was I having a "friendly" interaction with R, but I actually understood what it was telling me. Working with this program has been a strange conversational evolution. In the beginning, I didn't know how to talk to it and when I haphazardly managed a response from it, I didn't understand what it was telling me. Now, I've learned how to speak the R language (admittedly not fluently!) and the statistical language it spits back at me is making more and more sense everyday.
I also glanced back at some of the preliminary analyses I attempted on my data set before taking this class and it sent a shiver up my spine. It's amazing how far I've come from those frustrated fumblings with JMP 5.1 and SigmaPlot.
It's a good feeling to think that all of those long nights with Verzani, Gotelli, Ellison and R are paying off.
I also glanced back at some of the preliminary analyses I attempted on my data set before taking this class and it sent a shiver up my spine. It's amazing how far I've come from those frustrated fumblings with JMP 5.1 and SigmaPlot.
It's a good feeling to think that all of those long nights with Verzani, Gotelli, Ellison and R are paying off.
the Wonderful Wiki...
This blog is dedicated to the Wiki.
It has been such a wonderful supplement to the texts and my normal class notes. For someone just learning biostatistics, sometimes the class seems a bit fast paced and I have trouble catching everything. Several times I have found myself needing to solve a problem whose solution I only vaguely remember from something we discussed or an exercise we did in class. Most of the time, I am able to browse the Wiki and find either the answer or a good hint to point me in the right direction.
I appreciate everyone's effort in keeping it up-to-date this semester. It has been a very valuable resource.
It has been such a wonderful supplement to the texts and my normal class notes. For someone just learning biostatistics, sometimes the class seems a bit fast paced and I have trouble catching everything. Several times I have found myself needing to solve a problem whose solution I only vaguely remember from something we discussed or an exercise we did in class. Most of the time, I am able to browse the Wiki and find either the answer or a good hint to point me in the right direction.
I appreciate everyone's effort in keeping it up-to-date this semester. It has been a very valuable resource.
Wednesday, April 11, 2007
Cocktail-Making-Contests & Statistical Analysis
On Friday night I attended a surprise, birthday, cocktail-making-contest party for a girl in my lab named Genoveva. The idea was that party goers would compete to whip up the drink that the birthday girl liked the best. Everyone brought the fixins for their concoctions and mayhem ensued...
Later in the evening after Genoveva had tried all of the drinks, I noticed two people (both PhDs) huddled over a sheet of paper, scribbling columns of numbers and names of drinks onto a sheet of paper. When I asked them what they were doing, they said, "We're figuring out the results of the cocktail-making-contest. " Amused by their dedication to this analysis, I listened in on their calculations for a while.
They had one column of values for Genoveva's "score" of the drink on a scale of 1-10. The second column was a percentage of how much of the drink she had actually consumed. I couldn't hear everything they were saying, but I gathered that they were using the percent consumed as a covariate with drink score to determine who the true winner of the contest was, because, presumably, if she did not finish all of the drink, then she couldn't have really like it that much. I noticed that they did not consider confounding factors, such as how many drinks she'd had before she tried each drink, presentation, how many drinks she was being offerred at once, whethor or not she cleansed her palette with water between drinks, etc. However, as far as cocktail-making-contest analysis goes, I'm willing to bet that this was one of the most advanced calculations ever done.
I leaned over to the person next to me and whispered, "Who invited these nerds?".
Later in the evening after Genoveva had tried all of the drinks, I noticed two people (both PhDs) huddled over a sheet of paper, scribbling columns of numbers and names of drinks onto a sheet of paper. When I asked them what they were doing, they said, "We're figuring out the results of the cocktail-making-contest. " Amused by their dedication to this analysis, I listened in on their calculations for a while.
They had one column of values for Genoveva's "score" of the drink on a scale of 1-10. The second column was a percentage of how much of the drink she had actually consumed. I couldn't hear everything they were saying, but I gathered that they were using the percent consumed as a covariate with drink score to determine who the true winner of the contest was, because, presumably, if she did not finish all of the drink, then she couldn't have really like it that much. I noticed that they did not consider confounding factors, such as how many drinks she'd had before she tried each drink, presentation, how many drinks she was being offerred at once, whethor or not she cleansed her palette with water between drinks, etc. However, as far as cocktail-making-contest analysis goes, I'm willing to bet that this was one of the most advanced calculations ever done.
I leaned over to the person next to me and whispered, "Who invited these nerds?".
Monday, April 9, 2007
ANOVA and my circle
Heidi's presentation last week on ANOVA was my first real introduction to a statistical analysis that I probably should have familiarized myself with a long time ago. Finally having these concepts explained to me in plain English (well, as close as you can get with this stuff, I suppose) made me realize that for years I've heard and read this term over and over without really understanding what it meant. This got me thinking about something a professor once told me: Everything we know can be represented by the inside area of a circle, everthing we don't know would be the infinite area outside of the circle and everything that we realize we don't know would be the circumference of the circle.
Therefore, when we know little, we often think we know nearly everything. The more we learn, the more we realize we don't know. Only those who know a lot realize how little they really know.
Therefore, when we know little, we often think we know nearly everything. The more we learn, the more we realize we don't know. Only those who know a lot realize how little they really know.
Wednesday, March 28, 2007
DDIG
Well, I finally turned in my NSF dissertation improvement grant that I had to write for my Processes of Science in Ecology and Evolutionary Biology class! It was due at 5 pm today and I hit send on the e-mail just seconds before 5:01! Phew!
It is very uncustomary for a first semester grad student to have to write a grant like this, but I suppose it was a growing experience and I've learned a lot about the process.
One thing I realized is that I have a long way to go before I will be able to determine what kinds of statistical analyses to apply to my research. When I presented the material on experimental designs and statistical analyses, it seemed like such a neat little formula... all you have to know is if your independent variable and dependent variable are continuous or categorical and VOILA! you have the perfect recipe for your statistical analysis!
But it's not always that simple when you are trying to pick up a legacy project and work with a design that has been psuedoreplicated and has many uncontrollable confounding factors!
I still have so much to learn...
It is very uncustomary for a first semester grad student to have to write a grant like this, but I suppose it was a growing experience and I've learned a lot about the process.
One thing I realized is that I have a long way to go before I will be able to determine what kinds of statistical analyses to apply to my research. When I presented the material on experimental designs and statistical analyses, it seemed like such a neat little formula... all you have to know is if your independent variable and dependent variable are continuous or categorical and VOILA! you have the perfect recipe for your statistical analysis!
But it's not always that simple when you are trying to pick up a legacy project and work with a design that has been psuedoreplicated and has many uncontrollable confounding factors!
I still have so much to learn...
Thursday, March 8, 2007
Posting Graphs From "R" to Your Blog For Dummies
Hello Everyone!
For those of you itching to post your graphs from "R" onto your blogs, here are the steps I took to do it (Be aware that there may be a more efficient way, but this is what has worked so far for me):
1) Create your graph in "R"
2) Right click the graph and select "copy as bitmap"
3) In the "Start" menu, select "Programs" and then "Accessories". Click on the "Paint" program.
4) In Paint, click on the "select" tool. It will look like a box made out of dotted lines (probably in the upper left hand corner of the sceen).
5) Right click in the center of the blank part of the screen and click paste.
At this point, your graph should appear on the screen. You can use the text and drawing tools in Paint to add more detail or explaination to your figures.
6) Save the file as a bitmap on your computer.
7) Sign in to your blog.
8) Click "View Blog"
9) In the top right corner, click on "Customize" (the location of this may vary depending on what layout you selected for your blog)
10) On the new page, click "Add a Page Element"
11) You will have several options to choose from. Select the "Add to Blog" option under the space designated to adding pictures.
12) Browse your files to find your graph the same way you would add an attachment to an e-mail. You also have the option of adding a title and comment on the picture.
13) Click "save" and "preview".
Voila! Your graph should be posted! :)
For those of you itching to post your graphs from "R" onto your blogs, here are the steps I took to do it (Be aware that there may be a more efficient way, but this is what has worked so far for me):
1) Create your graph in "R"
2) Right click the graph and select "copy as bitmap"
3) In the "Start" menu, select "Programs" and then "Accessories". Click on the "Paint" program.
4) In Paint, click on the "select" tool. It will look like a box made out of dotted lines (probably in the upper left hand corner of the sceen).
5) Right click in the center of the blank part of the screen and click paste.
At this point, your graph should appear on the screen. You can use the text and drawing tools in Paint to add more detail or explaination to your figures.
6) Save the file as a bitmap on your computer.
7) Sign in to your blog.
8) Click "View Blog"
9) In the top right corner, click on "Customize" (the location of this may vary depending on what layout you selected for your blog)
10) On the new page, click "Add a Page Element"
11) You will have several options to choose from. Select the "Add to Blog" option under the space designated to adding pictures.
12) Browse your files to find your graph the same way you would add an attachment to an e-mail. You also have the option of adding a title and comment on the picture.
13) Click "save" and "preview".
Voila! Your graph should be posted! :)
Subscribe to:
Posts (Atom)
