normality

  1. B

    2-way ANOVA Normality Requirements

    Greetings, My objective is to conduct a 2-way anova (equal sample sizes/246 samples) in R. After running the Shapiro-Wilk normality test on the residuals, I am getting a p value of =.0011 which signifies that the distributions are not normally distributed. However, the histogram of errors and...
  2. M

    What is the role of the test statistic? [I'm not talking about the p-value]

    For example when Shapiro-Wilk test shows the statistic .945, df=12, p-value=.563 I know it's 'not significant' and I retain the H0 hypothesis, but I also have to write about the test statistic (.945), so what does it mean, when is it high, when is it low, comparing to what? Regards, Chris
  3. J

    confusion on terminology

    I could use some confirmation or correction on something basic that has been confusing me for a while. It has to do with "normal" and steps in modeling. Normality is for residuals (people already helped me with this in a previous thread) and this comes after fitting a model. In the beginning of...
  4. alfred

    Normality of a dataset

    Hello, In SPSS, which is the difference between the Kolmogorov-Smirnoff test under Analyze->Descriptive Stats->Explore and under Analyze->Non Parametric Tests->1 sample K-S? I always thought that the first one includes the Lilliefors correction and is more precise, but in principle the second...
  5. G

    Linear regression with non-normal data?

    It is my understanding that for linear regression both data sets must be normally distributed. One of my two sets of data (x) is normally distributed, but the second (y) has some values that could be outliers. When I make a histogram of my y data it looks something like this: (If the...
  6. L

    When to assume Normality

    I am working with a rather large sample (approximately 120). Typically, I would not have any issues justifying normality due to the large sample size and that the Central Limit Theorem would allow me to make that justification. However, of the 120 or so samples, there are about 8 extreme...
  7. B

    Violation of normality assumption for One Way Anova - Non parametric test?

    Hoping somebody can help with this? Recently we conducted a small study with ten participants. Each participant completed the same two tests, 'Test A' and 'Test B', during one session. Five particpants (Group AB) performed test A first, while the remainder performed test B first (Group BA)...
  8. S

    Normality Assumption

    Say there is 100 observations, but these observations are equally broken into 2 genders and 5 cities. When creating a qq plot or just checking normality by the S-W statistic, can the 100 observations be tested all at once or does the data need to be broken out by genders or even the five cities?
  9. J

    Confusion on what level should data follow normality

    Hi everyone. I'm experiencing some confusion as to what level the data should be normal. For instance, in an unpaired data set, where some vitamin is the main factor (given or not given) applied to a population of mice, you are interested if their blood sugar level is differing between the...
  10. R

    Transforming Variables

    I have several different variables. The majority of the variables were positively skewed and therefore I did a log10 transformation to make them more normal. However, two of the variables were quite normal already and now after log10 are more negatively skewed. In order for me to do some...