# Questions tagged [qq-plot]

A qq plot (or quantile quantile plot) is a scatterplot of the quantiles of two distributions. QQ plots are useful for comparing distributions.

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### I have applied many statistical tests to my data, but still cannot determine normality

I have run multiple tests to determine normality on my dataset, but I am unsure which one to adhere to, especially since my histograms, density plots, and QQ plots leave much to be desired in terms of ...
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### How to interpret a qq plot of uniform distribution whose slope is greater than 1

I am trying to interpret a qq plot of a uniform distribution in R where the plot is as shown in the image. The qq lines are a kind of straight but the slope of these lines way greater than the 45 ...
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### Distribution looks roughly normal on a q-q plot, but has a p-value of 0.0 for the Shapiro-Wilk normality test. How to interpret? [duplicate]

The distribution is as follows: However the Shapiro-Wilk test yields a p-value of 0.0 and a W statistic of 0.9. There are over 7,000 values in the sample. Note, the quantile values have been ...
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### Trouble selecting q-q plot settings with statsmodels. Do any of these plots properly compare the sample quantiles to theoretical normal quantiles?

I have an array of over 6,000 data points and am trying to show whether they follow a normal distribution. Statsmodels (the library I'm using to generate plots) gives the option of using a 45-degree ...
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### Does the maximum likelihood estimate give the optimal line of fit in a QQ plot?

Many analysts attempt to fit a distribution for a random variable by a. estimating the parameters with maximum likelihood then b. assessing the quality of the fit to the distribution by inspecting a ...
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### Distribution and variable analysis

I am doing a statistical test (program used is SPSS). On the basis of distribution and sample size, I have to chose the correct variable analysis. I also have to justify every decision. I have two ...
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### Does this need to be transformed? If, yes, how?

My data is collecting deposition of particles from the atmosphere once a month for 11 months at two sites. I am testing to see if my two sites' data are normally distributed so I can determine what T-...
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### Help me understand this qqplot

I have plotted the qqplot of the residuals that my model generates with the python module statsmodel sm.qqplot(data, line ='r') and it looks like this The points are placed on a straight line but ...
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### How do I interpret this QQ plot?

I am calculating a multiple regression with a sample of 128 and I was wondering, what distribution would best describe this residuals qq plot? It seems like a a Poisson-distribution to me, is it ...
1 vote
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### Q-Q plots and normality: Can I use ANOVA?

I want to use an ANOVA for my analysis (2x3 design). I can decide if I can safely use parametric tests. The two samples results: Shapiro-Wilk p<.001) and Q-Q plots don't seem to be normally ...
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### Evaluating goodness-of-fit for GARCH models in R with QQ-plots (rugarch package)

I'm currently working with multivariate GARCH representations of time-series for financial data using the rmgarch R package. This package in turn uses the well-...
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### How to define the line to fit in Q-Q plot?

I'm trying to figure out if my data follows a normal distribution and if it contains outliers. I have plotted the histogram and now I would like to plot the quantile-quantile (Q-Q) plot. My point is, ...
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### 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?
692 views

### Equally spaced points on x-axis in exponential distribution probplot/qqplot

I have a sample distribution and want to check if it is exponential. For that I am trying a qqplot and probplot. ...