# logistic regression

1. ### Logistic regression- categories

I am very new into Spss and spent a few hours to understand logistic regression. :shakehead I could not understand the relationship between 0 referance catogory and 1 valued category in logistic regression. For example, If dependent variable is school happiness ( 0 for yes 1 for no)...
2. ### Help with variable selection in logistic regression using a small dataset

Hello. I have a relatively small data-set looking at a binary outcome of death after a medical procedure. There are 102 patients total in the data-set, and 26 deaths. I am interested in looking at correlates of death. I first calculated univariate odds ratios, and have a list of 11...
3. ### Cox PH regression on fixed-interval (1, 2, 5-year) survival

Dear all, I am co-author on a manuscript on a study which follows a group of patients from a certain diagnosis and studies risk factors for survival. The main author has chosen to analyze fixed-interval survival rates (1, 2 and 5-year survival) and to compare the rates between two groups of...
4. ### Alternatives for logistic regression?

Hey everyone! I need some help because I am not really happy with the data analysis for my thesis. I am investigating the prognostic power of 3 quantitative and 2 qualitative variable on a dichotomous outcome. First off I wanted to know which set of variables is the best to predict the...
5. ### Logistic regression: dummy variables not significant, what next?

Hi, I'm running a logistic regression to try a predict landslides in SPSS using a categorical variable (vegetation type) with 6 possible values. In the results, the variable as a whole is significant although a couple of the dummy variables have p-values > 0.05 and thus are not significant...
6. ### I need help on Analysing multiple response categorical outcome

Dear all, I am interested to learn the effect of my predictors [ Categorical and continuous ] on the outcome variable [ multiple categorical variable]. My study is to investigate whether socioeconomic variables of my respondents have any effect on the type of welfare assistance they...
7. ### Logistic Regression: Interpreting Continuous Variables

Hi All, I had a couple of questions about interpreting odds ratios for continuous variables in logistic regression. I've done some significant digging online and in textbooks and I'm left thinking that my questions are so basic that they answers aren't explicitly stated anywhere. Although I'm...
8. ### Logistic regression controlling for variables vs. layer in crosstabs

Hi everyone, I would like to know how SPSS controls for variables in logistic regression in order to report the correct "controlled" OR. The specific case which bothers my is as follows: Lets say I have one IV tumor size which is either small tumor size or large tumor size the other IV...
9. ### Assessing outliers in a proportion

Hi all, Just wondering how one would assess outliers in the following: At the start of a two week period, people were asked to nominate a number of good deeds that they would perform in the next two weeks (N). At the end of the two weeks, they report how many they actually perform (C)...
10. ### Unbalanced dependent sample and intercept correction

Hi, I’m running a logistic regression analysis in SPSS and wanted to ask about the sample values for the dependent variable (landslide presence). My dependent variable is binary and has observed values of 1, or presence of landslides (252,204 cases, 86% of the sample), and 0, or absence of...
11. ### How to test dependent means with unequal sample size? Weighted Paired T-test?

Does a Weighted Paired T-test exist? I am comparing the percent of a population that are juvenile between 'Autumn' and 'Spring' at many sites. The Sample size (n) is variable among the sites and between the seasons. Sample data: Site___Fall %__n_____Spring %__n...
12. ### Predicted probabilities from logistic regression

Hi, I have carried out logistic regression in STATA to adjust for several patient characteristic variables that are thought to affect my outcome. I used the predict function to get estimates of the predicted probability of a positive outcome for each patient. Ultimately I would like to get...
13. ### Assumptions independent variables when just want to control/adjust for - less strict?

Is it true that when one just want to control for/adjust for in linear og logistic regression models, the variables one wants to control for/adjust for does not have to meet the assumptions of these models? For instance, if one wants to control for age, sex and education (common confounders)...
14. ### cross validation

Hi, I need some help with the following problem: I have a group of patients and I would like to classify them either in responders/non-responders to a certain treatment. For each person in the group a certain variable X was evaluated. By the use of ROC curves I have calculates the...
15. ### evaluating statistical difference between model coefficients: 2 different models

Hello, I have two logistic regression models with the same dependent and independent variables. The only difference between the 2 models is the way the data are aggregated: one model is based on census tracts, and the other on parcels. I want to determine whether there is a statistically...
16. ### Likelihood of Purchase - Proper Method

Hi Everyone, I'm trying to determine the odds of a product succeeding in a given area. After doing some research it seems that similar problems have been solved using Logistic Regression, but I'm still not a hundred percent clear on how it would work. Here's an example of how I was...
17. ### Logistic regression. How to combine classes in a mullticategorical variable?

Hi, I’m preparing some data with a view to carry out a multivariable logistic regression. The dependent variable is LANDSLIDES, i.e. occurrence, and is dichotomous (YES/NO). The independent variables are a collection of environmental factors, such as VEGETATION, SLOPE, ELEVATION, and...
18. ### Improvement of predicitve power in logistic regression - when is it significant?

I've posted this in another forum before but didn't get answers, so I try it here again I'm running a hierarchical logistic regression to find out if/how block 2 improves the predicted power in addition to block 1, so what I need is the value that is equal to ΔR2 in blockwise multiple...
19. ### 4 Vowel Intensities, Amplitude Spectrum of EEG - Multiple Logistic Regression?

I have EEG recordings of the neural response to speech (a male vowel with a fundamental frequency of 100Hz). The vowel was presented to each subject (n=15) at four different intensities (55dB, 65dB, 75dB, and 85dB), and I ran FFTs and pulled the amplitude at all of the harmonics of the...
20. ### Logistic Regression vs. Probit Regression

What are the key differences between Logistic and Probit regression? How does one decide which of them is relevant to a problem?