Loading in 5 sec....

Dr Paul Lambert and Professor Vernon Gayle University of Stirling PowerPoint Presentation

Dr Paul Lambert and Professor Vernon Gayle University of Stirling

- 132 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' Dr Paul Lambert and Professor Vernon Gayle University of Stirling ' - muncel

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

We do have existing tools, facilities and expert experience to help us…but we don’t make a good job of using them efficiently or consistently So the ‘significance’ of DM is about how much better research might be if we did things more effectively…

Key Variables: Social Science Measurement and Functional Form Presentation to: ‘Interpreting results from statistical modelling – A seminar for Scottish Government Social Researchers”, Edinburgh, 1 April 2009

Dr Paul Lambert and Professor Vernon Gayle University of Stirling

Key variables

Key Variables: Social Science Measurement and Functional Form

Key variables

‘Beta’s in Society’ and ‘Demystifying Coefficients’

- Dorling, D., & Simpson, S. (Eds.). (1999). Statistics in Society: The Arithmetic of Politics. London: Arnold.
- Irvine, J., Miles, I., & Evans, J. (Eds.). (1979). Demystifying Social Statistics. London: Pluto Press.
- Famous works on critical interpretation of social statistics tend to have a univariate / bivariate focus
- Measuring unemployment; averaging income; bivariate significance tests; correlation v’s causation

- But social survey analysts usually argue that complex multivariate analyses are more appropriate..
- Critical interpretation of joint relative effects
- Attention to effects of ‘key variables’ in multivariate analysis

Key variables

- “A program like SPSS .. has two main components: the statistical routines, .. and the data management facilities. Perhaps surprisingly, it was the latter that really revolutionised quantitative social research”[Procter, 2001: 253]
- “Socio-economic processes require comprehensive approaches as they are very complex (‘everything depends on everything else’). The data and computing power needed to disentangle the multiple mechanisms at work have only just become available.”[Crouchley and Fligelstone 2004]

Key variables

Large scale survey data: 2 technological themes statistical routines, .. and the data management facilities. Perhaps surprisingly, it was the latter that really revolutionised quantitative social research” We work overwhelmingly through individual analysts’ micro-computing Specialist development of very complex analytical packages for very simple sets of variables

- We’re data rich (but analysts’ poor)
- Plenty of variables (a thousand is common)
- Plenty of cases

- impact of mainstream software
- Pressure for simple / accessible / popular analytical techniques (whatever happened to loglinear models?)
- Propensity for simple ‘data management’

Key variables

Survey research: Access, manipulate & analyse patterns in variables (‘variable by case matrix’)

Key variables

Critical role of syntactical records in working with data & variables

Reproducible (for self)

Replicable (for all)

Paper trail for whole lifecycle

Cf. Dale 2006; Freese 2007

- In survey research, this means using clearly annotated syntax files
(e.g. SPSS/Stata)

Syntax Examples:

www.longitudinal.stir.ac.uk

Key variables

Stata syntax example (‘do file’) variables

Key variables

Some comments on survey analysis software for analysing variables..

- Data management and data analysis must be seen as integrated processes
- Stata is the most effective software, as it combines advanced data management and data analysis functionality and makes good documentation easy
- For an extended example of using Stata, concentrating on variable operationalisations and standardisations:
- Lambert, P. S., & Gayle, V. (2009). Data management and standardisation: A methodological comment on using results from the UK Research Assessment Exercise 2008. Stirling: University of Stirling, Technical paper 2008-3 of the Data Management through e-Social Science research Node (www.dames.org.uk)
E.g. “do http://www.dames.org.uk/rae2008/uoa0108recode.do”

E.g. “use http://www.dames.org.uk/rae2008/rae2008_3.dta, clear”

- Lambert, P. S., & Gayle, V. (2009). Data management and standardisation: A methodological comment on using results from the UK Research Assessment Exercise 2008. Stirling: University of Stirling, Technical paper 2008-3 of the Data Management through e-Social Science research Node (www.dames.org.uk)

Key variables

Working with variables and understanding variables..‘variable constructions’

- Meaning?
- Coding frames; re-coding decisions; metric transformations and functional forms; relative effects in multivariate models
- Data collection and data analysis
- Cf. www.longitudinal.stir.ac.uk/variables/

- processes by which survey measures are defined and subsequently interpreted by research analysts

Key variables

β variables..’s - Where’s the action? How we chose between alternative measures How much data management we try

- If we have lots of variables, lots of cases, yet often quite simple techniques and software, the action is primarily in the variable constructions…
- The example of social mobility research – see Lambert et al. (2007)

(or bother with)

Plus other issues in how we analyse & interpret the coefficients from the models we use (..elsewhere today..)

Key variables

i) Choosing measures variables..

See (2) below

- A sensible starting point is with ‘key variables’
- Approaches to standardisation / harmonisation
- {Lack of} awareness of existing resources
See (3) below

- Influence of functional form

Key variables

ii) Data management – e.g. recoding data variables..

Key variables

ii) Data management variables..– e.g. Missing data / case selection

Key variables

ii) Data management – e.g. Linking data variables..

Linking via ‘ojbsoc00’ :

c1-5 =original data / c6 = derived from data / c7 = derived from www.camsis.stir.ac.uk

Key variables

Aspects of data management… variables..

- Manipulating data
- Recoding categories / ‘operationalising’ variables

- Linking data
- Linking related data (e.g. longitudinal studies)
- combining / enhancing data (e.g. linking micro- and macro-data)

- Secure access to data
- Linking data with different levels of access permission
- Detailed access to micro-data cf. access restrictions

- Harmonisation standards
- Approaches to linking ‘concepts’ and ‘measures’ (‘indicators’)
- Recommendations on particular ‘variable constructions’

- Cleaning data
- ‘missing values’; implausible responses; extreme values

Key variables

‘The significance of data management for social survey research’see http://www.esds.ac.uk/news/eventdetail.asp?id=2151 and www.dames.org.uk

- The data manipulations described above are a major component of the social survey research workload
- Pre-release manipulations performed by distributors / archivists
- Coding measures into standard categories
- Dealing with missing records

- Post-release manipulations performed by researchers
- Re-coding measures into simple categories

- Pre-release manipulations performed by distributors / archivists

Key variables

Data Management through e-Social Science research’(DAMES – www.dames.org.uk) Why is e-Social Science relevant?

- Supporting operations on data widely performed by social science researchers
- Matching data files together
- ‘Cleaning’ data
- Operationalising variables
- Specialist data resources (occupations; education; ethnicity)

- Dealing with distributed, heterogeneous datasets
- Generic data requirements / provisions
- Lack of previous systematic standards (e.g. metadata; security; citation procedures; resources to review/obtain suitable data)

Key variables

Working with variables – further issues research’

- Re-inventing the wheel
- …In survey data analysis, somebody else has already struggled through the variable constructions your are working on right now…
- Increasing attention to documentation and replicability
[cf Dale 2006; Freese 2007]

- Guidance and support
- In the UK, use www.esds.ac.uk
- Most guidance concerns collecting & harmonising data
- Less is directed to analytically exploiting measures

Key variables

Key Variables: Social Science Measurement and Functional Form

Key variables

Key variables and social science measurement Form

Defining ‘key variables’

- Commonly used concepts with numerous previous examples
- Methodological research on best practice / best measurement
[cf. Stacey 1969; Burgess 1986]

ONS harmonisation ‘primary standards’ http://www.statistics.gov.uk/about/data/harmonisation/primary_standards.asp

Key variables

Key variables: concepts and measures Form

Key variables

Key variables –Standardisation Form

- Much attention to key variables involves proposing optimum / standard measures
- UK – ONS Harmonisation
- EU – Eurostat standards
- Studies of ‘criterion’ and ‘construct’ validity
- Standardisation impacts other analyses
- Affects available data
- Affects popular interpretations of data

Key variables

- “a method for equating conceptually similar but operationally different variables..”[Harkness et al 2003, p352]
- Input harmonisation[esp. Harkness et al 2003]
‘harmonising measurement instruments’ [H-Z and Wolf 2003, p394]

- unlikely / impossible in longer-term longitudinal studies
- common in small cross-national and short term lngtl. studies

- Output harmonisation (‘ex-post harmonisation’)
‘harmonising measurement products’ [H-Z and Wolf 2003, p394]

Key variables

More on harmonisation operationally different variables..”[esp. HZ and Wolf 2003, p393ff]

- Numerous practical resources to help with input and output harmonisation
- [e.g. ONS www.statistics.gov.uk/about/data/harmonisation ; UN / EU / NSI’s; LIS project www.lisproject.org; IPUMS www.ipums.org ]
- [Cross-national e.g.: HZ & Wolf 2003; Jowell et al. 2007]

- Room for more work in justifying/ understanding interpretations after harmonisation

Key variables

- “the degree to which survey measures or questions are able to assess identical phenonema across two or more cultures”[Harkness et al 2003, p351]

Key variables

“Equivalence is the only meaningful criterion if data is to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

[HZ and Wolf 2003, p389]

Key variables

Harmonisation & equivalence combined to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

- ‘Universality’ or ‘specificity’ in variable constructions
Universality: collect harmonised measures, analyse standardised schemes

Specificity: collect localised measures, analyse functionally equivalent schemes

- Most prescriptions aim for universality
- But specificity is theoretically better
- Specificity is more easily obtained than is often realised
- Especially for well-known ‘key variables’

Key variables

Working with key variables - speculation to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

a) Data manipulation skills and inertia

- I would speculate that around 80% of applications using key variables don’t consult literature and evaluate alternative measures, but choose the first convenient and/or accessible variable in the dataset
- Data supply decisions (‘what is on the archive version’) are critical

- Much of the explanation lies with lack of confidence in data manipulation / linking data
- Too many under-used resources – cf. www.esds.ac.uk

Key variables

Working with key variables – speculation to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required” b) Endogeneity and key variables We have only scratched the surface of understanding key variables in multivariate context and interpretation

- ‘everything depends on everything else’ [Crouchley and Fligelstone 2004]
- We know a lot about simple properties of key variables
- Key variables often change the main effects of other variables
- Simple decisions about contrast categories can influence interpretations
- Interaction terms are often significant and influential

- Key variables are often endogenous (because they are ‘key’!)
- Work on standards / techniques for multi-process systems and/or comparing structural breaks involving key variables is attractive

Key variables

An example: Occupations to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

- In the social sciences, occupation is seen as one of the most important things to know about a person
- Direct indicator of economic circumstances
- Proxy Indicator of ‘social class’ or ‘stratification’

- Projects at Stirling (www.dames.org.uk)
- GEODE – how social scientists use data on occupations
- DAMES – extending GEODE resources

Key variables

Stage 1 - Collecting Occupational Data (and making a mess) to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

www.geode.stir.ac.uk/ougs.html to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required”

Key variables

Occupations: we agree on what we to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required” should do:

- Preserve two levels of data
- Source data: Occupational unit groups, employment status
- Social classifications and other outputs

- Use transparent (published) methods[i.e. OIR’s]
- for classifying index units
- for translating index units into social classifications
for instance..

- Bechhofer, F. 1969. 'Occupations' in Stacey, M. (ed.) Comparability in Social Research. London: Heinemann.
- Jacoby, A. 1986. 'The Measurement of Social Class' Proceedings from the Social Research Association seminar on "Measuring Employment Status and Social Class". London: Social Research Association.
- Lambert, P.S. 2002. 'Handling Occupational Information'. Building Research Capacity 4: 9-12.
- Rose, D. and Pevalin, D.J. 2003. 'A Researcher's Guide to the National Statistics Socio-economic Classification'. London: Sage.

…in practice we don’t keep to this... to be compared from one context to another. However, equivalence of measures does not necessarily mean that the measurement instruments used in different countries are all the same. Instead it is essential that they measure the same dimension. Thus, functional equivalence is more precisely what is required” Numerous alternative occupational information files Inconsistent translations to social classifications – ‘by file or by fiat’ Dynamic updates to occupational information resources Strict security constraints on users’ micro-social survey data Low uptake of existing occupational information resources

Inconsistent preservation of source data

- Alternative OUG schemes
- SOC-90; SOC-2000; ISCO; SOC-90 (my special version)

- Inconsistencies in other index factors
- ‘employment status’; supervisory status; number of employees
- Individual or household; current job or career
Inconsistent exploitation of Occupational Information

- (time; country; format)
- Substantive choices over social classifications

GEODE provides services to help social scientists deal with occupational information resources

- disseminate, and access other, Occupational Information Resources
- Link together their (secure) micro-data with OIR’s

Key variables

For example: ISCO-88 Skill levels classification about OUGs…

Key variables

and: UK 1980 CAMSIS scales and CAMCON classes about OUGs…

Key variables

Existing resources on occupations about OUGs…

Popular websites:

- http://www2.warwick.ac.uk/fac/soc/ier/publications/software/cascot/
- http://home.fsw.vu.nl/~ganzeboom/pisa/
- www.iser.essex.ac.uk/esec/
- www.camsis.stir.ac.uk/occunits/distribution.html
Emerging resource: http://www.geode.stir.ac.uk/

Some papers:

- Chan, T. W., & Goldthorpe, J. H. (2007). Class and Status: The Conceptual Distinction and its Empirical Relevance. American Sociological Review, 72, 512-532.
- Rose, D., & Harrison, E. (2007). The European Socio-economic Classification: A New Social Class Scheme for Comparative European Research. European Societies, 9(3), 459-490.
- Lambert, P. S., Tan, K. L. L., Gayle, V., Prandy, K., & Bergman, M. M. (2008). The importance of specificity in occupation-based social classifications. International Journal of Sociology and Social Policy, 28(5/6), 179-192.

Key variables

Using data on occupations – further speculation about OUGs… Growing cross-national comparisons Treatment of the non-working populations

- Growing interest in longitudinal analysis and use of longitudinal summary data on occupations
- Intuitive measures (e.g. ever in Class I)
- Lampard, R. (2007). Is Social Mobility an Echo of Educational Mobility? Sociological Research Online, 12(5).

- Empirical career trajectories / sequences
- Halpin, B., & Chan, T. W. (1998). Class Careers as Sequences. European Sociological Review, 14(2), 111-130.

- Intuitive measures (e.g. ever in Class I)

- Ganzeboom, H. B. G. (2005). On the Cost of Being Crude: A Comparison of Detailed and Coarse Occupational Coding. In J. H. P. Hoffmeyer-Zlotnick & J. Harkness (Eds.), Methodological Aspects in Cross-National Research (pp. 241-257). Mannheim: ZUMA, Nachrichten Spezial.

- Seldom adequate to treat non-working as a category
- ‘Selection modelling’ approaches expanding

Key variables

Occupations as key variables about OUGs… When choosing between occupation-based measures…

- Extensive debate about occupation-based social classifications
- Document your procedures..
- ..as you may be asked to do something different..

- They all measure, mostly, the same things
- Don’t assume concepts measure measures
- Lambert, P. S., & Bihagen, E. (2007). Concepts and Measures: Empirical evidence on the interpretation of ESeC and other occupation-based social classifications. Paper presented at the ISA RC28 conference, Montreal (14-17 August), www.camsis.stir.ac.uk/stratif/archive/lambert_bihagen_2007_version1.pdf .

Key variables

Key Variables: Social Science Measurement and Functional Form

Key variables

‘Functional form’ Form

The way in which measures are arithmetically incorporated in analysis

- Level of measurement (nominal, ordinal, interval, ratio)
- Alternative models and link functions
- Other variables and interaction effects

Key variables

a) Levels of measurement and the desire to categorise Form Metrics are better for functional equivalence

- Categories are easier to envisage / communicate
- Much harmonisation work ≡ locating into categories
- Appearance of measurement equivalence
- But functional equivalence is seldom achieved

- E.g. Standardised income
- How to deal with categorisations?
- The qualitative foundation of quantity [Prandy 2002a]

Key variables

Example: categorisation and the scandalous use of collapsed EGP/NS-SEC…!

- Ignores heterogeneity within occupations
- Defines and hinges on arbitrary boundaries
- Creates artefactual gender differences

Key variables

The scaling alternative… EGP/NS-SEC…!

- Many concepts can be reasonably regarded as metric
- cf. simplified / dichotomisted categorisations

- Comparability / standardisation is easier with scales
- Complex / Multi-process systems are easier with scales
- Structural Equation Models
- Interaction effects

- Growing availability/use of distance score techniques
- Stereotyped ordered logit [‘slogit’ in Stata]
- Correspondence Analysis
- Latent variable models

- …But, scaling seems to be seen by some as a wicked, positivistic activity..!

Key variables

Practical suggestions on the level of measurement EGP/NS-SEC…!

- It’s rare not to have a few alternative measures of the same concepts at different levels of measurement
Good practice would be to

- try alternative measures and see what difference they make
- consider treatment of missing values in relation to measurement instrument choice
- Engage as much as possible with other studies

Key variables

b) Alternative models and link functions EGP/NS-SEC…!

- The functional form of the outcome variable(s) is of greatest importance (influences which model is used)
- ‘Link functions’ perform the maths to allow for alternative functional forms of the outcome variable
- See [Talk 1] for popular alternative models

Key variables

Practical observations on link functions EGP/NS-SEC…!

- Social scientists are unduly conservative in choosing between alternative models
- [We tend to favour binary or metric outcomes and single process systems]
- Substantively, this isn’t ideal
- Pragmatically, it’s no longer necessary

Key variables

Substantive risks (of conservative model choice) EGP/NS-SEC…!

- Attenuated findings
- Concentrate on certain category contrasts
- Ignore or exacerbate extremes of distribution

- Mis-specification
- Ignore / mis-measure relevant β’s
- Ignore / over-emphasise other contextual patterns

- Endogeneity
- ignoring multiprocess system may bias results
(e.g. selection bias)

- ignoring multiprocess system may bias results

Key variables

Pragmatics of model choice EGP/NS-SEC…!

- General rapid expansion in model functionality in statistical packages
- Stata stands out for it wide range of data management and data analysis functionality
- E.g. ‘statsby’; ‘est table’; ‘outreg2’; ‘estout’ facilitate testing and comparing related models with different combinations of variables

Key variables

c) Other variables and interaction effects EGP/NS-SEC…!

- A very important influence on one RHS coefficient is what else is in the RHS and what it is interacted with
Some brief comments on:

- Offsets (constraints)
- Interactions
- Logit models’ fixed variance

Key variables

A comment on ‘offsets’ EGP/NS-SEC…!- for comparisons between regressions, it is sometimes suitable to force the coefficients of some variables (e.g. controls) to have a certain fixed value- Below example (predicting income) using ‘cnsreg’ in Stata, e.g.: regress lninc fem age femage matrix define mod1m=e(b) scalar fem_coef=mod1m[1,1] constraint def 1 fem=fem_coef cnsreg lninc fem age femage mcamsis, constraints(1)

Key variables

Advice on Interaction Effects EGP/NS-SEC…!

- Start with main effects – get a good idea how they work
- Be careful how you fit interaction effects
- Often appealing substantively
- In practice not always significant (especially higher order)
- Hard to interpret higher order interactions
- Over-fit - check for replication (e.g. in other datasets)
- Always wise to formally test interactions (cf. armchair critics)
- Best to construct your own interaction variable(s) and maybe fit them as a single X (especially complicated categorical interactions)

Key variables

The fixed variance in logit: EGP/NS-SEC…!linear cf. categorical outcomes

GHS Data

OLS: Y = age left education (years)

Logit: Y = Graduate / Non Graduate

X Vars

Female

4-category social Class

(Advantaged; Lower Supervisory; Semi-routine; Routine)

Age (centred at 40)

Regression Estimates EGP/NS-SEC…!

Key variables

Linear Regression Models EGP/NS-SEC…!

- 1 unit change in X leading to a b change in Y
- The b is consistent – minor insignificant random variation (survey data)
- As long as the X vars are uncorrelated
(a classical regression assumption)

Key variables

Logit Model EGP/NS-SEC…!

- Estimates on a logit scale
- The b estimates a shift from X1=0 to X1=1 leads to a change in the log odds of y=1
- Even when the X vars are uncorrelated, including additional variables can lead to changes in b estimates
- The b estimates the effect given all other X vars in the model
- Fixed variance in the logit model (p2/3)

Key variables

Summary – Social science measurement and functional form EGP/NS-SEC…!

- We argue that the route to better critical understanding of variable effects combines complex analysis with many mundane, prosaic tasks in checking data
- ANALYSIS: Coefficient effects in multivariate models; multi-process models; understanding interactions; etc
- DATA MANAGEMENT: Re-coding data; linking data; missing data mechanisms; reviewing literature
- Seldom central to previous methodological reviews
- Cf. www.dames.org.uk

Key variables

References EGP/NS-SEC…!

- Abbott, A. (2006). Mobility: What? When? How? In S. L. Morgan, D. B. Grusky & G. S. Fields (Eds.), Mobility and Inequality. Stanford University Press.
- Bosveld, K., Connolly, H., Rendall, M. S., & (2006). A guide to comparing 1991 and 2001 Census ethnic group data. London: Office for National Statistics.
- Burgess, R. G. (Ed.). (1986). Key Variables in Social Investigation. London: Routledge.
- Crouchley, R., & Fligelstone, R. (2004). The Potential for High End Computing in the Social Sciences. Lancaster: Centre for Applied Statistics, Lancaster University, and http://redress.lancs.ac.uk/document-pool/hecsspotential.pdf.
- Dale, A. (2006). Quality Issues with Survey Research. International Journal of Social Research Methodology, 9(2), 143-158.
- Dorling, D., & Simpson, S. (Eds.). (1999). Statistics in Society: The Arithmetic of Politics. London: Arnold.
- Freese, J. (2007). Replication Standards for Quantitative Social Science: Why Not Sociology? Sociological Methods and Research, 36(2), 2007.
- Harkness, J., van de Vijver, F. J. R., & Mohler, P. P. (Eds.). (2003). Cross-Cultural Survey Methods. New York: Wiley.
- Hoffmeyer-Zlotnik, J. H. P., & Wolf, C. (Eds.). (2003). Advances in Cross-national Comparison: A European Working Book for Demographic and Socio-economic Variables. Berlin: Kluwer Academic / Plenum Publishers.
- Irvine, J., Miles, I., & Evans, J. (Eds.). (1979). Demystifying Social Statistics. London: Pluto Press.
- Jowell, R., Roberts, C., Fitzgerald, R., & Eva, G. (2007). Measuring Attitudes Cross-Nationally. London: Sage.
- Lambert, P. S., Prandy, K., & Bottero, W. (2007). By Slow Degrees: Two Centuries of Social Reproduction and Mobility in Britain. Sociological Research Online, 12(1).
- Prandy, K. (2002). Measuring quantities: the qualitative foundation of quantity. Building Research Capacity, 2, 3-4.
- Procter, M. (2001). Analysing Survey Data. In G. N. Gilbert (Ed.), Researching Social Life, Second Edition (pp. 252-268). London: Sage.
- Schneider, S. L. (2008). The International Standard Classification of Education (ISCED-97). An Evaluation of Content and Criterion Validity for 15 European Countries. Mannheim: MZES.
- Stacey, M. (Ed.). (1969). Comparability in Social Research. London: Heineman.

Download Presentation

Connecting to Server..