A Q–Q plot (or quantile quantile plot) is a scatterplot of the quantiles of two distributions. Q–Q plots are useful for comparing distributions.
Questions tagged [qq-plot]
331 questions
4
votes
1 answer
How to interpret this qqplot?
I wonder how to interpret this plot. I know, in general, that a qqplot depicts the quantiles of the data against the quantiles of the normal function.
How do I apply this to this plot?
Ben
- 3,443
3
votes
1 answer
Is it poissble to quantify the results of a Q-Q plot? (and does it make sense to?)
I have recently come across Q-Q plots and their usefulness in regards to visually inspecting whether a data sample follows a particular distribution.
Is there a way of quantifying the results of a Q-Q plot, to remove the subjectiveness of a visual…
user27119
- 308
- 1
- 17
3
votes
1 answer
interpreting Q-Q plot of a GWAS
In the attached q-q plot obtained from a genome-wide case/control study, the negative log of the p-values are plotted on the x (observed) and y (expected) axis.
Few SNPs at the extreme distribution deviates from the expected null distribution.…
Sam
- 31
- 1
- 2
2
votes
1 answer
What is y-axis on QQ plot?
I have a simple question about QQ plots in simple linear regression, but I am a bit confused about the plot: depending where i look the y axis is different: it can be either 1) residuals 2) standardized residuals 3) the actual independent variable.…
yuliaUU
- 303
2
votes
0 answers
interpretation of the slope of the qq plot
Reading https://seankross.com/2016/02/29/A-Q-Q-Plot-Dissection-Kit.html (one of the first results about interpreting qq plots) I find myself confused about the slope of the qq plot
It is my understanding that, to take a qq plot (for simplicity, with…
josinalvo
- 375
2
votes
2 answers
How to interpret qq plot "not on the line"?
What does it mean for my model diagnostics if my qq plot looks like this:
As you can see .... "off the line".
user162068
1
vote
1 answer
What does a flat qq-plot mean?
I was looking at some newly gathered data comprised of reading times measured in ms and I decided to plot the observed values prior to cleaning the data to see to what extent the data is normally distributed. I was quite surprised to see this…
amp
- 23
- 4
1
vote
0 answers
What does this QQplot tell us?
For a multivariate data set, I test normality on the marginals, and I get plots like above.
That's not my actual plot.... mine is not that obvious, the middle part is actually quite straight.... but the sharp decline/rise near the ends is the same…
Aeo
- 11
1
vote
0 answers
Interpretation of qq plot and normality
I am doing some multivariate regression. When I plot QQnorms to check my model assumptions (errors normally distributed), I get
Question: How do you interpret the above? Are the normality assumptions completely off? What's with those "breaks" near…
Imean
- 11
0
votes
0 answers
Is this normal QQ plot light or heavy tailed? First QQ plot I'm trying to analyse on my own
I think if it wasn't for the outliers on the tails, I'd be sure this normal QQ plot is light tailed but I'm not sure.
I'm aware I can use formal tests to find out, but I was told statisticians like to analyse plots without having to resort to tests…
user409634
- 1
- 1
0
votes
1 answer
QQ Plot interpretation
I wanted to investigate if my data is normally distributed with a QQ Plot. I'm not quite sure if the deviations from the theoretical plot are too big to crate a bland-altman plot?
C K
- 51
0
votes
1 answer
An explanation of the choice of QQ-line in a normal QQ-plot
The standard precedure for making a QQ-line in a normal quantile-plot is to draw a line through the first and third sample quantile.
My question is why?
If data follows a normal distribution, then sample quantiles should lie approximately on a…
0
votes
1 answer
Approximating location and scale from QQ-plot
So I'm solving old exams in preparation for my statistical data analysis exam and came by this question.
"b) Using the QQ-plot of the location-scale family that you have selected under part a, determine the location a and scale b…
0
votes
1 answer
How would you judge this qq plot? Distributional assumptions? Outliers?
Looking for some help. Here's my qq plot. I already deleted the most extreme outliers, but some remain. Also, what about the distributional assumption?
user163189
0
votes
0 answers
Normal QQ-plot interpretation
I seek help interpreting this qqplot.
Am I correct that data points near the mean are reasonably normal, but data points away from the mean tend to be too far off, therefore the data is fat-tailed?
Secondly the data appear to be symmetric (unskewed)…
user3817704
- 333