non-parametric

  1. S

    Parametric or non-parametric for 2 sets of data being compared one normal one not

    Hi folks, I am in a dilemma and maybe one of you can help. I have 2 sets of data, one from a control group and one from an experiment group. Each group took a test before and after a period of time and difference calculated. When checking for normality within the data via Anderson-Darling I...
  2. T

    Comparing three groups that have been analysed by Friedman's ANOVA

    Dear all, I have been struggling with the following problem and would be extremely grateful for some help. :confused: I have three groups of participants. For each participant I have six measurements for my experimental manipulation. I want to know whether there is an interaction of...
  3. G

    Help needed for a difficult scenario!

    I would appreciate help to understand how to appropriately analyze the following data. I have 3 groups: n1= 105, n2= 105, n3=15 (yes, just 15) Groups n1 and n2 are related (i.e siblings), thus not independent of each other as the data are under genetic influence; group n3 is not related to...
  4. M

    Seek confirmation for robust approach of describing non-parametric data set:confused:

    I’ve spent considerable time researching (on this site and elsewhere) for an appropriate statistical descriptor for a non-parametric (non-normally distributed) data set. I think I have the answer but would love any feedback as this is not an area of strength for me. TASK / DATA DESCRIPTION...
  5. I

    Kruskall-Wallis: what can we do if not significant?

    Hi all, I have a general question regarding Kruskall-Wallis test: When Kruskall-Wallis test DOES NOT yield significant results, can we still run Mann-Whitney tests with specific pairs of the conditions? If those pairs are significant, can we consider those results? Thanks a lot in...
  6. R

    ANCOVA when variances are not equal?

    I am currently writing a 4th year freshwater biology report analysing data collected on the length and weight of fish from 2 sites, collected over 3 years. We need run an ANCOVA checking Weight v Length/Site(SPSS, weight=dependent, site=factor, length=covariante). After checking...
  7. M

    Trying to prove significant difference between algal biovolume data

    Hello everyone I would like if possible to ask a question regarding a part of the statistical analysis in my MSc project: Following the sampling of the inlet and outlet of a stormwater pond at different times for different types of phytoplankton I wish to make comparisons of time same...
  8. M

    What method shoudl I inthose cell biovolume data

    Hello everyone! I am wiring a masters project involving counting algae and I am having a difficulty finding what is the right method to do the following comparisons on the biovolume data in this picture bellow: To test if there is a significant difference between the pairs Inlet 1-...
  9. R

    Plotting Medians Vs Means: non-parametric data

    Hi, I'm a PhD student who has been spending a lot of time lately analysing data (as seems to norm!) - a lot of my data sets fail normality tests, although show significant differences in the rank of means. My question, however, is what is the best way to represent such data? I originally...
  10. Y

    Is count data for parametric analysis or non-parametric analysis?

    Hi, In our paradigm, animals are presented with an stimulus and we count the number of calls they make. I believe the number of calls is discrete variable and count data. When we do an anlayis on these data, do we do parametric analysis or non-parametric analysis? For example, we...
  11. J

    Working with a distribution of outcomes from discrete events

    Hello, I have a data series that result from a long (2,950) series of discrete events. Roughly half of the events ended with a value of exactly -1, the other half are continously distributed between 1 and positive infinity. There are no values between 1 and -1. A histogram would look...
  12. M

    2-way ANOVA on non-normal, hetergeneous data

    I'm trying to analyze growth data from chicks, and I need to perform the equivalent of a 2-way ANOVA (2x2 design, unequal sample sizes), but my data are heavily skewed with heterogeneous variances, and transformation, which I avoid when possible, isn't helping. I've searched for alternative...
  13. M

    Parametric vs. non-parametric test.

    Dear all, group 1: treatment A group 2: treatment B thickness of the skin was compared between group 1 (n=20) and group 2 (n=20) I have used a non-parametric Mann-Whitney test resulting in a highly significant difference. Now, the reviewer of my paper has rejected the submission...