Linked Questions

1 vote
0 answers
3k views

Interpretation of qq plot and normality [duplicate]

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 ...
Imean's user avatar
  • 11
3 votes
1 answer
956 views

How can I visually determine the normality of interval data through a Q-Q Plot? [duplicate]

When dealing with interval data coming from questionnaires using Likert-Scales, I want to be able to determine the normality of the data in question. Some of the answers here on Cross Validated have ...
Omar Eldahan's user avatar
1 vote
0 answers
367 views

What does this QQplot tell us? [duplicate]

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 ...
Aeo's user avatar
  • 11
1 vote
0 answers
68 views

Fail normality test but the qqplot is a straight line [duplicate]

I am using SAS 9.4 . My aim is to find out whether my residual is normal or not, so i type this: ...
Gillian Cheung's user avatar
245 votes
5 answers
513k views

How to interpret a QQ plot?

I am working with a small dataset (21 observations) and have the following normal QQ plot in R: Seeing that the plot does not support normality, what could I infer about the underlying distribution? ...
JohnK's user avatar
  • 20.8k
39 votes
9 answers
9k views

What is the relationship between $Y$ and $X$ in this plot?

What is the relationship between $Y$ and $X$ in the following plot? In my view there is negative linear relationship, But because we have a lot of outliers, the relationship is very weak. Am I right? ...
PSS's user avatar
  • 843
15 votes
2 answers
48k views

How to draw fitted graph and actual graph of gamma distribution in one plot?

Load the package needed. library(ggplot2) library(MASS) Generate 10,000 numbers fitted to gamma distribution. ...
Ling Zhang's user avatar
9 votes
2 answers
7k views

Formal definition of the qqline used in a Q-Q plot

I'm doing some distribution fitting work and I'm looking at Q-Q plots and how they can be used visually to interpret goodness of fit. My data is heavy-tailed so I am looking at Weibull, log-normal, ...
Jonathan Dunne's user avatar
3 votes
3 answers
943 views

Not convinced about normality based on QQ plot, Shapiro and KS $p <0.001$

I have about 1000 data points, I'm trying to run a $t$-test because my points are divided in 2 groups and I want to compare them. The results of Shapiro-Wilk normality test: ...
Ana's user avatar
  • 71
16 votes
1 answer
1k views

Source for inter-ocular trauma test for significance

TL;DR: I am looking for the paper that proposed the following "inter-ocular trauma test for statistical significance". Longer version The idea of the proposed informal "test" is ...
Stephan Kolassa's user avatar
2 votes
2 answers
1k views

QQ plot result doesn't correspond to normality test [duplicate]

I am considering an ANOVA model for such data: ...
MaximeTars's user avatar
3 votes
1 answer
3k views

QQ Plot - drawn from a normal distribution?

I want to compare the distribution of the data from my model with normal distribution (since some previous works state that in comparison with normal dist. my data should have thicker tails). I ...
virusdotcom's user avatar
0 votes
2 answers
1k views

Using MLE to determine parameters for QQ plot

I just started playing around with a credit fraud dataset that I found online. I noticed that one of the variables looked something like this: Hey, that looks like a 3 parameter log-normal ...
user avatar
4 votes
2 answers
1k views

Interpretation of QQ-plots

I've read what they mean on a technical level, but I'm trying to build intuition related to a specific problem. So I have some data, a set of measurements. It's pretty curvy, looking like a cross ...
dreev2's user avatar
  • 69
0 votes
2 answers
3k views

Transform variables so residuals become normally distributed

I'm doing a project which involves multiple regression, and I'm aware (as far as I understand) that the residuals should be normally distributed with a constant variance. From my study, the residuals ...
Aerdennis's user avatar

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