Choosing a Statistical Test for Your IB Biology IA
HTML-код
- Опубликовано: 27 июн 2024
- CORRECTION AT 8:51: in the chart, 'Wilcoxon' and 'Mann Whitney' should be switched. Wilcoxon is the non-parametric version of the PAIRED t-test (not unpaired as the video suggests). Mann Whitney is the non-parametric version of the UNPAIRED t-test (not paired as the video suggests).
One small caveat: in broader mathematics, "number of bacterial colonies" would be treated as a **discrete variable**, which means the variable is numeric but it's restricted to certain values (and between those allowable values are gaps that the variable can't take on). But if you're plugging that variable into a regression or t-test/ANOVA model, then you're treating it as continuous. To quote minitab, which has great articles on statistics:
"If you have a discrete variable and you want to include it in a Regression or ANOVA model, you can decide whether to treat it as a continuous predictor (covariate) or categorical predictor (factor). If the discrete variable has many levels, then it may be best to treat it as a continuous variable. Treating a predictor as a continuous variable implies that a simple linear or polynomial function can adequately describe the relationship between the response and the predictor. When you treat a predictor as a categorical variable, a distinct response value is fit to each level of the variable without regard to the order of the predictor levels. Use this information, in addition to the purpose of your analysis to decide what is best for your situation."
support.minitab.com/en-us/min...
One big caveat: some may take issue with the terms 'relationship' and 'comparison' and the way I'm using them. Consider a medical researcher who is testing a new drug by comparing a treatment group with a placebo group. She might say: "the video says I'm doing a comparison of two groups. But I disagree; I believe I'm seeking a relationship/correlation between the drug and the therapeutic effect." So who is right--the video or the medical researcher? The fact is that comparisons can allow us to deduce relationships, and this creates ambiguity. In the video, the term 'relationship' perhaps should be interpreted very narrowly to mean: 'you're seeking a mathematical equation that relates the variables.' And the term 'correlation' should be interpreted narrowly to mean: 'you're seeking a number showing how correlated your two variables are.' These terms (comparison & relationship) describe what you're doing with the data and variables themselves, not the larger goals of the experiment.
Nothing can replace practice; the more you use these tests, the more you'll understand how they apply and what their limitations are. I'm not an expert on statistical tests. If you find other good explanations or sources that go into subtleties that the video overlooks, please share them in the comments!
Lastly, here's one of the most rigorous descriptions of what p-values are, from a true expert, Daniel Lakens: • What is a p-value? by ...
He has a course on Coursera called "Improving Your Statistical Inferences" that I highly recommend: www.coursera.org/learn/statis...
One small caveat: in broader mathematics, "number of bacterial colonies" would be treated as a *discrete variable*, which means the variable is numeric but it's restricted to certain values (and between those allowable values are gaps that the variable can't take on). But if you're plugging that variable into a regression or t-test/ANOVA model, then you're treating it as continuous. To quote minitab, which has great articles on statistics:
"If you have a discrete variable and you want to include it in a Regression or ANOVA model, you can decide whether to treat it as a continuous predictor (covariate) or categorical predictor (factor). If the discrete variable has many levels, then it may be best to treat it as a continuous variable. Treating a predictor as a continuous variable implies that a simple linear or polynomial function can adequately describe the relationship between the response and the predictor. When you treat a predictor as a categorical variable, a distinct response value is fit to each level of the variable without regard to the order of the predictor levels. Use this information, in addition to the purpose of your analysis to decide what is best for your situation."
support.minitab.com/en-us/minitab-express/1/help-and-how-to/modeling-statistics/regression/supporting-topics/basics/what-are-categorical-discrete-and-continuous-variables/
thank you very much for your generous response.
Good
@Raggul Kanakasabapathy, it sounds like it could go either way. I'm not an expert by any means, but I think you would decide whether to treat the independent variable as categorical vs continuous by asking questions like "do I expect a linear relationship between the input and output, such that more of the independent variable consistently leads to more/less of the dependent variable?" I think you can also ask questions like "for the purposes of my study, do I care about the *relationship* that the independent variable has to the dependent variable, or do I care about finding e.g. a single dose that is therapeutically significant?"
Do you have reasons to expect that salt has a linear relationship (positive or negative) with plant growth? Are you interested in the specific nature of that linear relationship (e.g., is your goal is to say "for every 1 g of salt, the leaves grow X cm longer")? If so, then it might make more sense to treat mass as continuous.
Alternatively, are you looking for whether a particular mass of salt exists which provides a statistically significant growth effect? Are there reasons why too little salt could inhibit growth, and too much salt could inhibit growth, but maybe there's a salt mass in the middle that could balance multiple biological factors and yield the most growth? If so, then it might make more sense to treat mass as categorical. The fact that you described 0 g of salt as the "control group" already suggests to me that you might be looking to compare salt vs. no salt, and the reason you have different amounts of salt is to help answer the question "do plants grow more effectively with salt than without salt?" In other words, having a control group suggests that you're not looking for the specific nature of a hypothesized linear relationship between amount of salt and amount of growth.
I've never taught IB Bio, but I did teach IB Physics. If you're writing an IB Biology IA, I would think it's worthwhile to explain how you're analyzing your data and justify why you chose to treat the independent variable as categorical vs. continuous. If you choose to treat mass as categorical, then you've got a categorical independent variable and a continuous dependent variable--what test would you use in that circumstance? If you treat mass as numerical, then both the IV and DV are continuous--what test would you use in that circumstance?
(By the way, you can still do a regression with a categorical independent variable, but that's not really done in IB Biology, and it sounds like this might not make sense in your case. Here's what it would entail. For each dose, you'd essentially have a different dummy variable that takes on a value of 0 or 1. So the variable m_1g would be 0 or 1, and the coefficient would tell you how much more/less growth the plant had compared to 0 g when 1 g of salt was added. The variable m_2g would similarly take on values of either 0 or 1, etc.)
Another quick thing--if you go the route of performing multiple t tests (to compare each salt mass to the control group), then you want to watch out for family-wise error. You can do a quick Google search to see what this is. This is usually dealt with by lowering the p value that you need in order to reject the null hypothesis. For example, if you do 5 t-tests, and you'd normally use p < 0.05 as your significance level, then you might instead calculate 0.05/5 and use p < 0.01 as the significance level for each test, since performing multiple tests increases the likelihood of a false positive. There are different ways to account for this family-wise error, and the appropriate approach depends on the class you're in and how rigorous the statistics element is.
@Raggul Kanakasabapathy Since it's an IA, I can't quite give you a direct answer--that will be up to you. All I'll say is that it sounds like you're saying you have a continuous IV, a continuous DV, and you seek the mathematical relationship.
if you go the route of regression, I have a few thoughts: (a) I think regression and mathematical relationships are less common in IB Bio IAs. Because of that, I recommend asking your teacher if you're on the right track and if you have a suitable topic, question, and statistical analysis approach. (b) If you go the route of regression, I think you will want to be careful about how you phrase your research question. If your understanding is that regression is appropriate when seeking a mathematical relationship between a continuous IV and a continuous DV, then you want to phrase your research question as seeking that *mathematical* relationship between the variables. (c) In all of it, the ultimate goal is to use the analysis as a mechanism to talk about in-depth Biology analysis. So if you find a negative linear relationship, then you want to use the Biology you've learned to try and explain, in depth, *why* that relationship exists. (d) Since I've never taught IB Bio, definitely have a conversation with your teacher about all of this. The advice I'm giving you is good for IB Physics, but I'm not sure how much of it translates over to Biology.
@Raggul Kanakasabapathy Hi Raggul, I was curious how your IA turned out! Were you happy with the final product?
Finally, the sky is clear....
This is perhaps the most simpliest and yet full tutorial I've heard on statistical tests LOL.....Well put together Daniel. Thanks
Thanks for the kind message! I'm glad it was helpful
FACTS
This is by far the best material about SPSS I've ever seen in my whole life. Throw 100$ SPSS books into trash can. This video is very beautiful in a minimalist way. Greetings from a procrastinator doctor, who is trying to hurry analysis at 07:00 AM for the finish date of a paper :-)
9:57 minute video vs 6 weeks of lectures...just wow!
An amazingly simple description of statistical tests. Thank you so much!
Wow! I cannot express how much I am grateful to you for making this video. I spent one week figuring out which suitable statistical test was for my case. THANK YOU
Thank you so much for this video! Simple, concise, well organised -- it's rare to see such a well-made tutorial to a somewhat confusing topic such as this, amazing :)
I have all this data I’ve collected for my masters thesis, I’ve been looking for a test to use for two days. This video, hands down, has just saved my life. THANK YOU!!!
how did it go
Man, this guy nailed it. I fumbled in my undergrad research. I wish this was available to me then. Thank you, Sir.
I watched so many videos on this topic. But this is the best explanation so far. Thank you so much
Im from the Linguistics field in this is still helpful for my thesis, thank you!
After struggling for years trying to figure out about the necessity of so many statistical tests, finally I have an overview of statistical tools an how to choose one from.
I fell in love with the way you explained both the qualitative and quantitative techniques.
Thanks Venu!
Thanks for making it super simple, clear, and easy to understand!
Thank you sooo much for this video! It saved my life!I spent so many days trying to understand which test I should use for my master's thesis. You explained VERY well and simple! Thank you again.
This video includes more data and has better educational content than what I learned in my MSc. Thank you Daniel.
The Simplest and Most Comprehensive Demonstration of Tests...Thank You
Thank you for this video. You did a great job of explaining the various statistical tests and their applicability.
For a broad perspective, this is a remarkable video. Nice work! This helps a lot
Thanks so much, Don!
From the bottom of my heart THANK YOU for this
Thank you! Was recommended for Business Data Analytics.
4:08 is particularly useful if you're wondering what sort of test to use (or, what it's called!) Chi-Squared / t-Test / Correlation.
Thanks man. Best explanation I've seen so far 👍
simply perfect and clear explanation . Thanks for your great effort
Simply the best and clearest explanation video.
This video has helped me more than my biology teacher, love you man
Glad it helped! I sympathize with IB Bio teachers! They're expected to teach statistics, but it's not part of the curriculum!
Beautifully explained and simplified...... keep going 👍🏾
Thorugh and simple to understand. Thanks
Statistics are so simple and easy to understand after your wonderful explanation. Thank you for this amazing video.
Stat is not easy subject 😭😒
Simple, easy and best and proper way to have quick notes
Very succinct and well put together. Thank you, Daniel!
Thanks to Allah.. I have found someone who is teaching the basics..I needed it badly
Hello. I need some help from you
@@asmasultana2732 yes
I'm glad it helped! I often need the basics too. This is a good starting place, but this video really does make some simplifications, and as you study more, you'll see that things aren't always so clear cut. I'm glad it helped!
The most simpliest and useful tutorial i ever heard and seen. Thank you soo much for giving us such a wonderful lessons. 😊😊😊
Best video I watched in statistics especially in experimental designs
Thank you very much for that simple and valuable information
Very brief and to the point. Great for a reasonable first overview of these topics. Thanks
I watched many videos on Hypothesis tests and always left with some sort of confusion. But you made it really simple. 🔥
Thanks for enlighten me on how to choose these statistical tests. I will be grateful to learn more.
half semester of my statistics class didnt give such comprehension, thank you for this well put video.
After struggling for years trying to figure out about the necessity of Sr many statistical tests, finally I have an overview of statistical tools an how to choose one from.
Great job! It helped a lot in explaining the basics! Nice work!
I like how the simplicity of your content, keep it up.
This video perfectly cleared everything up, thank you so much.
Awesome video! Thank you so much, Professor! Cheers from Brazil!
This video is so well made! Thank you for your effort. It's really helping us out.
Very glad to hear that! Check out the caveats I pinned at the top of the comments. Feel free to ask questions!
I'm in IB Sports Exercise and Health Science but this video helped a lot for choosing the test for my IA. Thanks!
So helpful. Thank you! The basics make it easy to understand everything
Wow this simplified everything so much, thank you
Great video, I understood the concept clearly.. thanks alot!
Bravo! It is just the thing I needed to refresh my background after a long break
Haters will say this clip is way too simple, I will respond yes that’s why it’s almost perfect.
This helped me a lot, and I'm taking a graduate level class. Thank you!
I don't know how you did it but you have helped me to know this better.
Beautifully explained Daniel. Thank you
Omg... I am a year 5 dental student and this vdo finally opened my mind...
This video basically summarized two semesters of my statistics subject ngl.
Reaffirmed what I am beginning to grasp. Thank you!
Thanks for the explanation. 👍 Appreciate your efforts.
Comprehensive and over simplified.A great video.
One of the best explanations. Thanks much.
Absolutely wonderful...!!!
The way to generalize test in a table is amazing!! Thanks! It really really helps a lot!
Glad it helped! Just don't miss the correction I mentioned in the description
Best teaching method
Very clear explanation. Thank you so much.
Glad it helped!
Thank u so much! Very helpful for newbies like me ^^
Best video on statistical tests
Sir you just nailed this video, you made me so damn clear about correlation. Thanks alot for your precious video😍
Best ever teaching technique....
This is so helpful, thank you!
Thank you very much for the simplest explanation
your english is impeccable. i can clearly hear the proper pronunciation and enunciation. Concept is well explained.
It's funny--I think people think I'm smarter than I am because I enunciate well :)
Thanks Daniel! This helped a lot!!
best ever discussion in truly simple way. love from Bangladesh🇧🇩🇧🇩🇧🇩
Thanks a lot for making me understand a lot better. Thank you once again.
I am not clear about which technique is used for the which study before observing this video. Now I clear about it . Thank you sir
As simple as it can be...Thank you so much
Very well explained! Thank you~
Thank you so much, this is really helpful. I am even able to understand my own research thoroughly without thinking what was the reason why is it not relationship based.
thank you!! i need to use this info in my bio enzyme productivity analysis thesis!
tysm!! i would've had a breakdown if not for your video 🤧 also, the dun dun dun at 0:08 made me laugh so thanks for that too
I wish you taught me Econometrics. Thank you for this.
currently doing my BIO IA. thank you
Crystal clear explanation!
Thank you!
Thank you❤️. You've really helped me a lot.
Very precise and clear
Very useful and clearly put information. Thanks
Best summary video ever!!
Thank you!!
@@danielm9463 The world needs an @danielm9463 full statistics course series. I’m taking a statistics for the social studies. I’ve watched tons of videos on RUclips. I’ve not seen a tutorial done this well. So, we need more! You’ve got a gift ❤️
@@dharris6357 ❤❤❤ thank you!! I would love to make a full stats video series and hope to have time for that some day soon. What types of topics do you think would be most useful? Given that you study stats in your class already, is it the big-picture overview that is most useful, or would it be helpful to have videos on the mechanics of e.g. how to do a t-test and why/how it gets modified when there are unequal sample sizes, unequal variances, etc.? Or is it more helpful have videos with big-picture overview / how to look at different scenarios and see which test would apply?
This helps me a lot. Im going to use this on my report
this helped me a lot, thank you
Excellent video
wonderful lecture
This was very helpful.thank u so much❤️
Thank u sir u made it so simple to understand excellent presentation with explaination. Thank u too much
Dude this is really helpful. Thanks
Great simple. Effective. Video. Love it
Very clear! Thanks !
Definitely I will make notes of this video.
I'm slow when it comes to math (like "if johnny has 5 apples" type slow) and this breakdown finally made things clear
Don't hesitate to post any questions you have about your work or what you're studying!
Sooo good I literally cried
Excellent explanation
Thank you for this video🙏✍