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Does data have to be normally distributed for P value?
Key Result: P-Value Because the p-value is 0.4631, which is greater than the significance level of 0.05, the decision is to fail to reject the null hypothesis. You cannot conclude that the data do not follow a normal distribution.
Should you log transform all variables?
You should not just routinely log everything, but it is a good practice to THINK about transforming selected positive predictors (suitably, often a log but maybe something else) before fitting a model. The same goes for the response variable. Subject-matter knowledge is important too.
What happens when errors are not normally distributed?
When errors are not normally distributed, estimations are not normally distributed and we can no longer use p-values to decide if the coefficient is different from zero. In short, if the normality assumption of the errors is not met, we cannot draw a valid conclusion based on statistical inference in linear regression analysis.
How to transform normal distribution to lognormal distribution?
Different methods exist for different distributions and maybe you will be able to achieve your goal without using techniques that strictly require Gaussian distribution. The code snippet below fits three different distributions on the sample data: lognormal, normal, and Weibull distributions.
Why is data in Figure 4 not normally distributed?
The data in Figure 4 resulted from a process where the target was to produce bottles with a volume of 100 ml. The lower and upper specifications were 97.5 ml and 102.5 ml. Because all bottles outside of the specifications were already removed from the process, the data is not normally distributed – even if the original data would have been.
When does the distribution of data become an issue?
If a practitioner is not using such a specific tool, however, it is not important whether data is distributed normally. The distribution becomes an issue only when practitioners reach a point in a project where they want to use a statistical tool that requires normally distributed data and they do not have it.