normality test

  1. Z

    ANOVA normality test

    Hello, I was wondering, how many assumptions of normal distribution must be violated to conduct a non-parametric test? In my opinion, in my dataset, only one assumption has been violated which is p<0.05. I think the first Q-Q plot looks ok but I am not sure. Also, I don't understand what the...
  2. S

    Normality test in data with multiple treatments

    Greetings. I have to test for normality to know if I go the ANOVA route or the Kruskal-Wallis route and I don't know how to go about it. I have an experiment with the setup shown in the attached image. I have several treatments, within each treatment I may or may not have independent reactors...
  3. L

    Normality is not assumed ( kolmogorov-smirnov sig level= 0.000)

    Currently, I'm doing a research using Beck Depression Inventory on 340 respondents from my university. Before I apply any parametric tests, I tested the normality first, however the normality is not assumed. So, I wondering is the data really not normal or the way I analyze it have problem ...
  4. B

    Why normality assumption needed?

    I often see that for parametric tests one assumption is that the population should be normally distributed. However if I understand correctly the central limit theory shows that the distribution of the sample means (the sampling distribution) has a normal distribution, irrespective of the...
  5. B

    Shapiro-Wilks significant, all other indicators NORMAL

    Hello everyone, I am checking my assumptions before running an ANCOVA, one of which is that the DV is normally distributed across all levels of the IV. MY IV is 3 groups (Ns of 32, 31, and 32) and my DV is a continuous variable from 1 - 5. Before splitting into groups, it looks normal and the...
  6. L

    Normality test

    I will use Normal probability plot or Shapiro-Wilk test for normality check. But is it that straightforward or there is some subtlety in this? Many Thanks
  7. T

    How To Test A Distribution For Normalcy

    I'm looking for Visual Basic source code that will, after entering the data of a distribution, test that distribution for being normal or 'almost' normal. Alternatively, I am looking for step by step instructions for such a test, so that I will be able to create the source code myself. Thanks.
  8. N

    help with Normality test?

    Hi all! this is probably a simple question; however, my statistics skills got a bit rusty and I cannot find an appropriate solution on the internet... This is the problem: Let X_1, ..., X_n be a series of values drawn from a normal distribution. All I know about them is their mean u=sum...
  9. R

    Degrees of freedom for Chi2 normality test

    I have found mixed information in regard to the number of degrees of freedom used to evaluate the chi2 statistics derived to check the normality of a given data set. In one case I found that df = Nbins - 3 and in other cases I have found df = Nbins-1 The idea of this test is to divide the...
  10. S

    Justify the use of KS over Shapiro and Wilk normality test

    Hello there. I am testing my data distribution for normality using both Shapiro Wilk and Kolmogorov and Smirnov tests in SPSS. S&W reveals that the data is not normally distributed whereas K&S shows its approximately normally distributed. How can i justify the use of K&S over S&W in order to...
  11. S

    Justify the use of parametric tests on non normally distributed data

    Hello there. I have 5 Likert scale questionnaires that have been answered by the same people who have been randomly selected (N=24) and i have the following problem: I first test the data distribution of each scale in order to determine what statistical analysis tests should i employ...
  12. S

    How to get the output using PROC MIXED for residual error to check for normality?

    I am using proc mixed for my analysis (RCBD), but don't know the SAS code for outputting the residual which I can use for checking normality. Can anyone help me with the SAS code? The code I'm using is: proc mixed data=A; class ID trt depth block; model LogNO3= trt| depth; random block...
  13. R

    Normalizing Skewed Data

    Hello, I'm a novice in stats, and I wanted to know how to normalize 'skewed' data. I work with SPSS and I went to transform>compute variable> and then I do a log transformation... However, when I run the normality tests, I am still getting a significance of .000 for both the K-S and...
  14. T

    Nonparametric test and ANCOVA

    Good day everyone. I'm a student who are currently doing her psychology research (final year project). I'm having an issue with my data being not normal. I have ran the test of normality(Shapiro Wilks test) using SPSS software and I found out that my p-value is 0.000 (not significant). And then...
  15. P

    Normality tests for SAS

    Hi All, I just ran the PROC MIXED for outputting the residual error in SAS [TO CHECK FOR NORMALITY] I am wondering if I need to look at Shapiro-Wilk or Kolmogorov-Smirnov tests? My sample size is 217 [repeated at 3 time points]. So, when I check for the normality of the residual error, do I...
  16. N

    ANOVA, residual normality assumptions

    Hi everybody, I would like to ask you something about the normality hypotesis on the residuals when performing an ANOVA. Do I have to check the entire residuals data set or, do I have to check normality of the residuals relative to each level of each IV (for example, 1 IV with 3 levels, 3...