You ay find helpful the book by "Using Multivariate Statistics" by Tabachnick and Fidell. It features a chapter about explorataory data analysis which includes the topic. http://www.pearson.ch/1471/9780205890811/Using-Multivariate.aspx.

I've also seen some papers published in the Annual Review of Psychology. For example: http://www.annualreviews.org/doi/abs/10.1146/annurev.psych.58.110405.085530?journalCode=psych.

I hope this helps.

Thank you Juan for the reference to the book as well as the reading, I will have a look at that to assist with the missing data handling techniques. Timo, thank you for your assistance, it helped shed light on the 'simply enter the mean score' idea. Many thanks.

There is actually a 'Missing Values' module you can purchase. The module is designed to assist in the identification of any patterns of missingness, estimate means, standard deviations, covariances, and correlations for different missing value methods, and ultimately impute data. I used the module a few years ago and it was quite helpful, though somewhat expensive.

Thanks so much Joseph, I will have a look into that.

1.0 using SPSS: Analyze > Missing values analysis... > Estimation > tick EM

2.0 EM is expected maximisation estimation technique to impute missing data. It also comes in handy with Little's MCAR test. You want this to be p > .05 for EM to work well.

3.0 There's a brief explanation in this document https://www.researchgate.net/publication/262151892_Introduction_to_SPSS

Article Introduction to SPSS

Thank you so much for your assistance, I greatly appreciate it.