If you already own a copy of MLwiN and have not upgraded to the latest version, please upgrade to MLwiN for free as this may solve some problems.

- Try our MLwiN user forum where we welcome all users to post enquiries
- You can also join the Multilevel Modelling discussion list
- If you have bought MLwiN, you may be entitled to email support. (You are entitled to free email technical support if you have bought MLwiN or
*MLn*(*except*the PhD version)- Note: If you are a UK academic and have downloaded the free version you are not entitled to free support.

- Resources for using MLwiN
- Our online course with its practical instructions for using MLwiN and other software

- Downloading MLwiN
- MLwiN 2.1/beta/trial/other versions
- Realcom
- MLwiN and operating systems
- Getting data in and out of MLwiN
- Large datasets
- Worksheets
- Sample size, significance testing and suitability of data
- Errors and crashes: Error messages during estimation/ implausible results
- Errors and crashes: crashes/problems opening MLwiN or worksheets
- Errors and crashes: Other errors/problems
- How do I…? Categorical variables
- How do I…? Commands and macros
- How do I…? Discrete response models
- How do I…? Longitudinal data
- How do I…? MCMC
- How do I…? Missing data
- How do I…? Parameters and parameter estimates
- How do I…? Partitioning variance and the intra-cluster correlation
- How do I…? Residuals
- How do I…? Standard errors
- How do I…? Using weights
- Miscellaneous

- For all questions about downloading and purchasing MLwiN please go to Ordering MLwiN FAQS

- Should I uninstall the MLwiN 2.10
**beta**version I have before installing a later version? - I already have MLwiN 2.10 beta but the
**upgrade**to the latest version will not work - What is the difference between the
**training**, the**trial**version and the**full**version? - Can I open
**SPSS/Stata/Minitab worksheets**using the training version of MLwiN?

- Does
**multiple imputation**in Realcom work with the free trial version of MLwiN? - Other problems with Realcom or
**Realcom-Impute**

- What are the MLwiN system requirements?
- Can I install MLwiN onto a
**Mac**or**Linux**system? - Is MLwiN compatible with versions of Windows later than 7?
- Does MLwiN make use of Multi-core/Multi-processor environments?
- Is it possible to run MLwiN on a
**Citrix**-desktop?

- How do I get
**data into**MLwiN? - How do I get
**data out**of MLwiN? - Are there any issues I should be aware of when opening my
**Stata/SPSS/Minitab**files with MLwiN 2.1? - Opening a .dta (
**Stata**) worksheet, I get the error message 'Duplicate name(RSTA)' - I'm trying to export a number of
**variables**from MLwiN, but only the first 5 appear in the text file

- How do I know MLwiN can handle the model based on my own data?
- I'm having problems importing a large dataset from
**SAS** - I'm having problems working with a large dataset in MLwiN. Does MLwiN have a limit to the
**size of dataset**that it can handle?

- How do I
**increase the worksheet size**? - Does each row correspond to a single record right across the MLwiN worksheet?
- Does it matter what
**order**the data appears in in the worksheet? - Other questions about worksheets

- Sample sizes for Multilevel Models
**MLPowSim**- Sample size, significance testing and suitability of data
- How can I calculate
**confidence intervals**in MLwiN? - What significance tests for both
**random and fixed parameters**are available in MLwiN? - How do I test whether
**two coefficients**are equal? - How do I test whether
**more than 2 coefficients**are equal? - How do I test if an interaction between a
**continuous and a categorical variabl**e is significant?

- How can I calculate

Go to **Errors and crashes** >>

- I get an error message when I run my model/ numerical problems
- I got an error message 'cannot allocate rmatrix(ws)(like)'
- I tried to run a binomial model and got an error message
- I tried to run a binomial model and got an error message (2)
- When do I allow
**negative variances**? - I get an error message 'wrong parameter…' when using MCMC
- When I get the error message "MCMC error 0315: prior variance matrix is not positive definitive" while running a multinomial model using MCMC, what exactly do I need to do to the numbers in C1096?
- I get an error message asking me to 'generate unique ID codes'. How do I do this?
- Implausible results or convergence problems
- MLwiN is giving the standard errors of parameter estimates as 0, but I know from comparison with other software packages that the standard errors should not be 0

- Why has MLwiN crashed?
- The European convention of using a comma as a decimal point causes MLwiN 2.10 Beta to crash when using the Intervals and Tests window
- MLwiN fails to open after changing the default worksheet settings
- When I run MLwiN I get the error message "Pre or Post file does not exist (post)"
- I have a worksheet saved on a network drive that I can't open using MLwiN
- When I try to open the worksheets for the
**LEMMA**course I get an error message - When I double click on one of the worksheets for the LEMMA course, it opens with notepad not MLwiN

- When trying to
**plot a graph**, I get the error message 'Failed to open Graphics Server' - Why has my data become
**corrupted**? - I can't get the
**LOGOn**command to work - I noticed a
**difference in values**I get between versions of MLwiN - Other errors/problems

- How do I update the category labels for a
**categorical variable**? - I've recoded a categorical variable, but the list of category codes I see when I press Categories has not been updated
- How do I get rid of an unneeded
**dummy**variable/ response category? - Other questions about categorical variables

- How can I easily save and run commands?
- When I work with MLwiN using the various windows, is there any way to record the commands that will do the same thing?
- I copied commands generated by MLwiN when I was using the GUI and pasted them into a
**macro**, but when I ran the macro I got an error message - Output from my macro is not appearing in the Output window
- Can I run my
**old macros**written in MLn under MLwiN? - Will macros written for version 2.02 work with earlier versions of MLwiN?
- I’d like to call MLwiN from the command line. Is that possible?
- Other questions about commands and macros

- How can I specify a
**binomial response**model using a macro? - What is the command for specifying the
**denominator**when fitting a binomial or multinomial model? - Why is the
**log-likelihood**value not displayed in the Equation Window when a Binomial or Poisson model has been fitted? - MLwiN gives different results to
**SAS**and**Stata** - How do I calculate
**variance functions for multinomial models**? - How do I interpret the estimates for the fixed part parameters in a
**Poisson**model? - Other questions about
**discrete response models**

- Does MLwiN need
**repeated measures**data to be in long or in wide format? - Is it possible to define an AR process for the random effects at level 1?
- When should I allow level 1 errors to be
**autocorrelated**? - Where are the
**time series macros**?

- Can I change the length of the burn-in without re-running the model?
- Running
**MCMC from a macro**doesn't appear to work

- How do I explore the patterns of missingness in my data? (PDF, 381kB).

This document shows how you can produce a list of all the patterns of missingness in your data together with information on how frequently each one occurs.

- Where is the
**model fitting**information stored in MLwiN? - Is it possible to output the error variance-covariance matrices for parameters?
- Is it possible to constrain parameters in MLwiN?
- How can I constrain
**random parameters**to zero? - How can I constrain
**fixed parameters**to zero? - How can I constrain parameters to values other than zero?
- How can I constrain
**two parameters to be equal**? - Other questions about parameters

**Partitioning variation**across levels - more information- Where can I find the
**random parameter matri**x in MLwiN? How do I use this to work out the residual ('unexplained') variance at each level? - How do I calculate the amount of variation at each level for
**nonlinear**models? - What is the
**intra cluster correlation**?

- My residuals column is too short
- Should the comparative SD output when I calculate the residuals be different for each row?
- Residuals slide presentation with voice-over plus transcript

**Sandwich estimators**for standard errors - more information- Can MLwiN produce robust standard errors?
- Other questions about standard errors

**What are weights**and how do I use them?- Is the weights facility in MLwiN still experimental?
**Differential weightings**- more information- How do I use weights in a
**multiple membership**model?

- My
**Names**window looks different to the screenshots in the training materials and I can't find all the buttons mentioned in the instructions - Is it possible to fit
**splines**in MLwiN? - Does each row correspond to a single record right across the MLwiN worksheet?
- My level 2 variables are being treated as level 1 variables
- MLwiN can no longer
**PRINT**windows