From: <arthur.gilmour_at_DPI.NSW.GOV.AU>

Date: Tue, 30 Oct 2007 19:46:09 +1100

Date: Tue, 30 Oct 2007 19:46:09 +1100

Dear Peter

*> I need to estimate the population mean (mu). I understand that mu can
*

*> be estimated from the following model if there is no singularity.
*

*> Y ~ mu c(site) c(group) c(site).c(group) !r site.group.rep tree
*

site.family

This would return the so called 'least squares' mean - i.e. the simple

mean of

the cells in the predicted site.group table regardless od the number of

observations. Such a mean can be a long way from the mean of the

population

which is weighted by the frequency in each cell.

*> If singularity exists, however, can I use the following PREDICT
*

*> statement to get the correct estimate of mu?
*

Y ~ mu site group site.group !r site.group.rep tree site.family

predict mu !present site group !average tree

One can argue about what is 'correct'. The issue really is what is

appropriate for your purpose.

There is a difference between this predict and the former 'mu' because

'tree'

is handled differently. Typically PREDICT will ignore random terms

(involving rep, tree, family)

Assuming a pedigree for 'tree' so that tree effects do not sum to zero,

the average of the tree effects

is added in, (as well as affecting the SE of the prediction - conditional

rather than marginal)

Without '!average tree', the predict statement will give the simple mean

of the site.group cells

that are present. If the data is unbalanced, is that the mean you want?

Alternatively

you may want some other weights. Look at the !PRWTS qualifier if so.

May Jesus Christ be gracious to you,

Arthur Gilmour, His servant .

Mixed model regression mapping for QTL detection in experimental crosses.

Computational Statistics and Data Analysis 51:3749-3764 now available at

http://dx.doi.org/10.1016/j.csda.2006.12.031

Profile: http://www.dpi.nsw.gov.au/reader/17263

Personal website: http://www.cargovale.com.au/

mailto:Arthur.Gilmour_at_dpi.nsw.gov.au, arthur_at_cargovale.com.au

Principal Research Scientist (Biometrics)

NSW Department of Primary Industries

Orange Agricultural Institute, Forest Rd, ORANGE, 2800, AUSTRALIA

fax: 02 6391 3899; 02 6391 3922 Australia +61

telephone work: 02 6391 3815; home: 02 6364 3288; mobile: 0438 251 426

ASREML 2 is now available from http://www.VSNi.co.uk/products/asreml

The ASReml discussion group is at ASREML-L_at_dpi.nsw.gov.au

To join it, mailto:arthur.gilmour_at_dpi.nsw.gov.au

Archives are at

https://gatekeeper.dpi.nsw.gov.au/Listserv/archives/asreml-l.html

Cookbook: http://uncronopio.org/ASReml

Proposed travel:

UK 28 Jan

USA 11-15 Feb

*><><><><><><><><><><><><><><><><><><><><><><><>
*

Received on Sat Oct 30 2007 - 19:46:09 EST

This webpage is part of the ASReml-l discussion list archives 2004-2010. More information on ASReml can be found at the VSN website. This discussion list is now deprecated - please use the VSN forum for discussion on ASReml. (These online archives were generated using the hypermail package.)