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Discovering Statistics

This is a group for users of my textbooks (and anyone else really) to discuss the books, post questions and so on.

Members: 225
Latest Activity: Apr 8

Discussion Forum

Compute contrast in repeated measure anova in R vs. SPSS 2 Replies

I am teaching statistics to students in psychology. My university used statistica and I want to change for R. Thus, I opened the book of Andy Field and followed all the instructions. No problem was…Continue

Started by Nicolas Stefaniak. Last reply by Nicolas Stefaniak Mar 14.

Assumptions associated with GLM in SPSS

Hello,I am new to this group and I have questions both general and specific about linear models.I’ve read the book "Discovering statistics using IBM SPSS statistics" 4th Edition, mostly.General…Continue

Started by Alexander Quent Jan 3.

difficulty in detecting interactions when effects are limited to a small number of groups 2 Replies

I am working on a study that includes a large number of groups, different doses and control groups. This study involved administering two drugs. The first drug was given as a pretreatment to block…Continue

Started by Josh Bugner. Last reply by Josh Bugner Dec 17, 2013.

Non-normality issue 3 Replies

Hello All,What do we do if the data is not normally distributed? Here is the issue:Data was collected from university students. Sample size above 200. SEM is intended to be used. We wanted to measure…Continue

Started by Ibrahim Al-Jubari. Last reply by Ibrahim Al-Jubari Oct 9, 2013.

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Comment by Sally Ransom on February 6, 2013 at 16:29

Hi all,

I'm very pleased to let you know that SAGE has recently set up a new Facebook page about all things Andy and Discovering Statistics, where we'll be posting news, free stuff, photos, videos, competitions and more. We've just posted the second video in our Ask Andy Anything series which is well worth a watch! Hope you can join us over there:

Comment by Charles C Moller on February 4, 2013 at 19:03

I'm sorry that I posted a new discussion item as a comment to this thread. I now understand where it should have gone.

Comment by Charles C Moller on February 4, 2013 at 17:43


I am new to R and am learning using DSUR. On page 78 it is suggested that we load a package called DSUR in order to have handy the functions in the book. The current DSUR package is not compatible with R v 2.15.2. Do we simply cut and paste from the book's website? Is there a new DSUR package out there that I have missed?


All the best,


C Moller

Comment by Sinfree Gono on October 11, 2012 at 18:16

Thanks Katie. Have sent to the group hoepefully with luck i will get some hints.

Comment by MJ on May 22, 2012 at 12:33

Hi everyone,

I am doing ROC Curve analysis to establish cut-off points for a scale. I calculated Youden's index to establish cut-off points, however to my despair, the Youden's index is equal for two of the scores:

Let's say my subjects could score between 10-20 on a scale and the Youden's index is the highest at 124.5 for scores 15 and 16 on this scale. I wonder what would be the best cut-off: 15 and 16?!
obviously sensitivity is higher on one score and the specificity for the other

Thank you for your help

Comment by Henry Steel on May 22, 2012 at 8:43

Dear Andy and All

I have a question about data transformations. Consider the following explanation written by Andy:

“As such, transforming the data won’t change the relationships between variables (the relative differences between people for a given variable stay the same), however, it does change the differences between different variables (because it changes the units of measurement). Therefore, even if you have only one variable that has a skewed distribution, you should still transform any other variable sin your data set if you’re going to compare differences between that variable and others that you intend to transform.”

My concern is the following: I understand Andy's argument about changing the units of measurement, but what will happen if you transform a variable that is normal? Will it become skewed? If so, what is the use then of transforming the skewed variable(s)? Maybe I am missing something. Looking forward to some advice.

Best wishes


Comment by Rafael Garcia on May 1, 2012 at 22:48


There's a decent description of post hoc tests here:

In short, different post hoc tests scale the F-ratio differently. Depending on how the F-ratio is distributed, you may end up with n.s. contrasts (common in Scheffe's method).

Comment by Mutasem Akour on May 1, 2012 at 22:27


I wonder how is it possible to get a significant omnibus F in one-way ANOVA, and getting no significant differences in a post hoc test ?

Comment by Mohamad Azwan Suroto on January 30, 2012 at 7:27

yey I am part of this group... 

Comment by Rebone Gcabo on December 5, 2011 at 9:01

Thank you so Much Oscar, will try  it.



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