transformation

Hi, After I calculated some multiple regressions I'd like to perform some simple regression trees to capture also some possible nonlinear trends and discontinuities in my data. My multiple regression model is something like: log(Y) ~ X1 + log(X2) + log(X3) The response and some of...

If two predictor variables transformed by the Johnson Transformation (see Minitab or Johnson 1949) are used in separate linear regressions (assuming the same response variable and sample sample size of predictors in each single predictor variable model) can the R-squared output of separate...

Hi fellow nerds :) My dependent variable had to be transformed by square root (so the residual plot would be normal). I usually use log10 transformations and then the B value (slope) translates into the percents of the dependent variable, but what do I read from a B=-,499 (P=0,015) of a...

Hi all, I have been discussing this topic all week with people in my department and I can't seem to get a straight answer. I also tried posting this thread in a non-psychology forum and received only a few straight of the textbook responses about positive skew. I was taught long ago that you...

Hi all, I have been discussing this topic all week with people in my department and I can't seem to get a straight answer. I was taught long ago that you should not necessarily transform a variable if the population distribution is expected to be skewed (for use in regression analysis). For...

How would I go about solving this? 1/nΣxi^2=100 and 1/nΣxi=2. Define yi=2xi+1 and find 1/nΣyi^2.

Hey all, Ok so I'm trying to compare the means of two sets of data using a 2-sample t-test. Unfortunately, both sets of data are non-normal. It appears box-cox or Johnson transforms will work, but my question is, wouldn't I need to transform both sets of data using the same transform...

Hi there, Basically, I am checking for outliers in a 'frequency of use' construct measured in number of weeks. Since the box plot was right-skewed, i conducted a log transformation via spss. Although, the result seemed fine but now I want to create boxplots for other constructs which are...

Hi, i have data on age (years) and a continuous variable (weight for example). I want o predict the age using a linear regression. However, i understand that age is discrete and therefore may not be directly used. So i log transformed both the age and the weight but now i checked the residuals...

I have two datasets, before and after the application of a treatment. The treatment is theorised to produce an increase in "factor x", and difference between the two datasets should be a positive value, however due to noise/error etc in the data some of the difference values are negative. In...

Hi everyone, I am trying to do a factor analysis of a group of drinking behavior variables, and some of them are highly positively skewed. I want to do a log transformation of these variables, but they are binary. I can't find anything that deals with whether this is a problem or not - but...

Hello, My response variables are derived from count data. I have the biennial winter population counts of a hibernating mammalian species (sites / n =226). My predictor variables are from two time steps (i.e. 1992 and 2001). I created my response variables from the following to correspond...

For data that may look linear but is in fact cyclical (time most commonly), is there like a sine function based data transformation that has been proven to work well? I feel kinda silly making dummy fields, and now that I'm playing around with multiple imputation, I'm worried that if I'm missing...

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...

Hello all, I'm doing upwind/downwind comparisons for air quality data. I recieved some feedback yesterday (thanks Simon!) that a paired t-test would probably be an appropriate way to compare hourly averages from two sites located about 1km apart. Also, that the data set is probably large...

Two-way ANOVA (with replication), how robust is robust? Hello all, I would like to see what the pain of a patient is before and after an opperation. But my data is not fitting the assumptions of ANOVA. I have read that ANOVA is robust, but how robust? I have data from patients who were...