I have been reading about Altman-Bland plots and I often read in papers that if the scores lie within the limits of agreement this represents adequate agreement. Yet, from Bland and Altman's work it appears that the limits of agreement must be sufficiently narrow, with the concept of sufficient varying depending on how precise one needs the instrument to be. Am I correct in this interpretation? Does this plot show adequate agreement?
Thank you!
https://preview.redd.it/jfnm143mn8v71.jpg?width=601&format=pjpg&auto=webp&s=7298af1c0cf48985e2cb5cbaaf7cb9fcda5943bb
I have two questions
- is mean and bias the same?
- if the bias is 6.1 what does that mean?
Thanks
Hello everyone !
An assumption of the Bland-Altman limits of agreement is that the differences are normally distributed. I have a variable I have to study by a Bland&Altman plot with a leptokurtic distribution.
Can I keep this kind of distribution (not so a-normal to me) to plot Bland&Altman analysis rather than transform my data and get a more complicated interpretation on the y-axe due to this transformation?
Hey there,
I'm just looking for some advice on how I should set my limits of agreement for Bland-Altman plots for my thesis.
As part of our thesis we conduct an experiment and write a scientific paper on it. The overview of ours is we want to create an injury screening test that better represents loading in basketball by comparing loading during a layup to loading during a drop jump and a stop jump. To determine which test show agreement clinically significant limits have to be set. The issue is this is novel data so acceptable limits of agreement have not been previously set in the literature.
One thing I thought to do use studies that have assessed the relationship between vGRF and injury during drop jumps and use this data to determine a limit. To give you the figures Leppanen et al., 2016 reported that those that got injured recorded peak vGRF of 1347+/-403N versus 1083+/-321N in the uninjured group.
Should I calculate the percentage difference of the GRF and the GRF-1SD for the injured group and then compare that to percentage difference of GRF and GRF+1SD to see at what point would there start to be false positives and false negatives and set the limit of agreement at the threshold?
This is a complete guess so any thoughts would be massively appreciated!
Stats are not my strong point at all so There is a very good chance I'm wayyyyyyyyy off here!
Need to make sure two gene expression measurement assays are equivalent. I'm told a Band-Altman plot is the way to go, and that makes total sense
https://en.wikipedia.org/wiki/Bland%E2%80%93Altman_plot
Where you want 95% of the data points to lie within +/- 2 standard deviations of the mea difference.
The question is - how many subjects (people) should we do this on? Also, each assay measures 20 genes, so it seems like by randomness we should expect at least one of those genes to NOT meet the 95% cut-off, but only due to chance...anyone have experience with this?
Hi!
I'm trying to use a bland-altman plot (pretty new to me) to compare the result values from two laboratory methods. I've calculated and set up everything with the exception of the confidence intervals (upper and lower confidence intervals) for the Limits of Agreement.
I'm struggling to understand paired t-tests, the different types, and what values I should use from them in calculating my confidence interval.
For example, even just using the Data Analysis toolpak in excel, I have 3 different t-Test options - Paired Two Samples for Means, Two-Sample assuming Equal Variances, and Two-Sample assuming Unequal variances.
I'm certain it's not unequal variances, since the two lab methods are being tested on the SAME sample. But does that mean I used paired two sample for means? or two-sample assuming equal variances?
Then when excel spits out the t-test, I'm uncertain which value I should use to calculate my confidence interval.
Any help would be fantastic. Lots of googling and reading has given me a lot of information, but I'm still VERY uncertain with HOW to proceed and WHY i'm making the right decision.
As far as I understand Bland-Altman plots are used to compare two different methods of measurement. But I have trouble to understand how the plot is interpreted.
Is it correct to assume that the closer the data points scatter around the line of the mean difference the smaller is the difference between both methods? What do the limits of agreement indicate and what does it mean if data points are outside of these limits? I've also seen 95% CI around the limits of agreement. What do these indicate? Thank you in advance.
Hello AskStatstics,
A while back I read about this method and how it should be used to complement ICCs, but I'm having a tough time determining when it's appropriate to use them. After some searching, I think that:
-you use them when comparing two methods of measurement
-you do not use them when you're assessing test-retest reliability of one method
Can someone who has used Bland-Altman plots before please confirm I have this right?
Many thanks!
Hello everyone,
I have a very simple question. I made a Bland-Altman plot to compare the results from two paired samples.
Is this correct to label the x-axis "Mean glycemia value of two paired samples" and the y-axis "Differences between glycemia values from two paired samples" ?
I know you have to use the mean as x-axis and the differences as y-axis for a Bland-Altman plot, but I'm not a native English speaker and I'm afraid to make a vocabulary or grammar mistake.
Thank you for your help !
Hi there,
I'm comparing the results from blood analysers. Historically we've only had two machines so bland-altman plots have been great as they show there's no bias as results change across the range. My question is, we now have three analysers, so is there a version of bland-Altman that is suitable for more than 2 measurements.
If there isn't I am guessing I could simply plot result (x-axis) vs difference from average of 3 results (y-axis) which would produce a similar graphical representation. Does this seem reasonable?
Hi /r/AskStatistics,
I'm hoping this is an appropriate sub to post this question. Feel free to suggest others if there's a better place, since this is more a theory question.
I'm a student currently working on a manuscript with an adviser. Our aim is to establish equivalence of values reported by a parent to estimates obtained by two different objective methods. Because we want to support the use of the parent-report method, we are comparing this method to one of the objective methods separately (so M1 vs. M2, M1 vs. M3). We've read extensively on the Bland-Altman method and subsequent articles that expand on this work. We have already conducted statistical analyses to support agreement between the methods (if necessary, I'll provide a basic summary of what we did), but our research has overwhelmingly suggested that Bland-Altman plots should at least be supplemented to support the agreement of two methods.
My question is how do Bland-Altman plots support the results of statistical tests? I understand that B-A plots can easily display constant or proportional bias, allowing us to eventually suggest "corrections," but this isn't the objective of our project. Since our aim is to support that more-or-less equivalent values are obtained from the methods, does saying "look how the values are clustered on the 0 difference line" suffice? Or am I missing something more sophisticated here?
My adviser has little experience working with B-A plots or equivalence testing in general, so I appreciate your feedback!
Some brief literature on the topic, if needed:
[Wiki] (http://en.wikipedia.org/wiki/Bland%E2%80%93Altman_plot)
[Assessing Agreement between two Methods of Clinical Measurement] (https://www-users.york.ac.uk/~mb55/meas/ba.htm)
Edit: formatting issues
Hey guys,
i have a question about the interpretation of a bland Altman diagram.
It has a linear trend so there is a systematic mistake, isn't it?Can I get more information out of this bland Altman diagram ?
It's about a comparison of two sensors. If they measure the same angle at the same time.
https://preview.redd.it/ujn6emr1nu981.jpg?width=640&format=pjpg&auto=webp&s=b798e657a7339c7bb552aa2ab82d4b63b2da66ef
Thanks for replying!
It's a remake of the comic strip / animated toon Popeye. From the special features on the Blu-Ray, it's specifically a remake of the COMIC. How did this get funded 50 years after the comic's debut?
The high point is either the cafe fight or boxing fight, with a lot of comic visual gags in a short period of time.
https://www.youtube.com/watch?v=Sn-qSWegNGA
There's an amazing shot where Popeye rolls away like a wagon wheel and I assume it was acheieved with a specially built wheel that looks like Popeye. Half the movie is basically the Harrison Ford Clickhole saga.
It's one of the worst plots I've seen. A completely reheated plot from other, better movies. Popeye needs to fall in love and find his father. Full on 2/10 plot for me.
Half of Shelley Duvall's lines as Olive Oyl are "ooooh" and she's amazing as the nagging 1930s love interest. Robin Williams' mumbling asides as Popeye are also funny.
With your hand on fast-forward or your phone, it's worth a look. The opening is intentionally less cartoonish, to allow Popeye to grow into a comic character. Probably why I found the first 15-20 minutes (leading up to the gag-heavy bar fight) so slow.
There's a Euro cut which is 93 minutes. Some good gags got cut which is a shame, since it should be the one to watch. It cuts the window scene (13 seconds, at 35m or 43m) which is unforgivable. My cut would include as much of the tooniness as possible while shortening the molasses-slow baby/father plot. The Disney EU recut is more about getting to the end of the plot while avoiding some of the toon silliness that doesn't advance the "plot".
https://www.reddit.com/r/blankies/comments/mxrec3/today_i_learned_the_ukeuropean_release_of_robert/
https://www.movie-censorship.com/report.php?ID=819543
Also cuts the Bluto I'm Mad song which has some toon destruction.
Good that Disney cut these for Europe:
- Sail/stay with me
- Pappy / mean large song
- For the love of god, 2 minutes quicker to the island
One person calls Popeye unsavable:
> For me, one example would be Robert Altman's Popeye. One can cut out all the dreadful songs by the usually dependable Harry Nilsson. One can even make cuts to pick up the pace of the film. But what the movie desperately cries out for is a knock-down, drag-out fight between Popeye and Bluto to match the best of their animate
... keep reading on reddit ➡I am interested in making bland Altman plots to show the agreement between measurements made by two labs. However, in all cases one lab made significantly more measurements than the other. For example, one lab reported 71 concentrations while the other only reported 21.
How do I handle the missing values? Is it possible to use limits of agreement in this case?
I am not a statistician. But I need to be able to understand and apply this statistical tool for a research internship. Here is the original paper: http://www.ncbi.nlm.nih.gov/pubmed/2868172
Halime does nothing major to the plot (correct me if I'm wrong), and was extremely boring to watch. Basically all she does, is cry about ertugrul going, and give birth to osman, gunduz and savci.
Every. Single. Time. "eRtUGrUL dOn't gOooOo." She has the same facial expressions every time, she barely contributes to the main plot other than romance and fighting with other woman. Just a boring character overall
Edit: Seems like ALOT of people disagree, which I expected, but, could anyone tell me some things that are good about her character. Most people are just saying no, or defending her, but I don't think anyone has yet said something good that she's done. To me (just my opinion btw), I feel like everyone is just simping for Halime, as she has nothing special about her. 0 acting. 0 character development. This is my opinion, you are entitled to yours.
