Scope and Contents Thomson comments briefly on Thurstone’s The Vectors of the Human Mind, pointing out that Thurstone uses a theorem proved by Burt. Thomson also refers Ledermann to articles he and Ledermann wrote for Psychometrika on boundary conditions, since this is something he wishes to write about in The Factorial Analysis of Human Ability. He informs Ledermann that he will be taking part in a discussion...

Scope and Contents

Thomson informs Ledermann that he has submitted his paper to the British Journal of Psychology, and has included a referral to a future article of Ledermann's.

Scope and Contents

Thomson discusses some areas of uncertainty he has regarding making back estimates of the scores z from the first few Hotelling factors, referring to Bartlett's estimates of the Thurstone common factors.

Thomson asks Ledermann whether the back estimates using the Hotelling method or Bartlett-Thurstone method are best. He has added a short post script at the end of his letter the next day stating M S Bartlett's method is best.

Scope and Contents Thomson tells Ledermann how pleased he is that he is that Ledermann is going to follow up his [Thomson's] paper for the British Journal of Psychology, and asks him to include material regarding multivariate selection. He talks about the various reading he has undertaken, referring to work by Bocher, Hotelling, and Turnbull; and discusses the connection between the correlation of orthogonal vectors produced by selection in the...

Scope and Contents

Thomson informs Ledermann that Burt, Spearman, and Myers are to be the other speakers at the Royal Society discussion he is participating in, and that he has asked if Ledermann and Emmett may attend as guests.

He refers to a geometrical discussion of Bartlett's form of estimation which he originally sent with the letter for Ledermann's comments. This has not survived in the collection.

Scope and Contents

Thomson informs Ledermann that he has sent Ledermann's paper to the British Journal of Psychology, with some minor corrections. He tells Ledermann he should take some time off when his Mother visits him, and apologises for not being able to invite him to Glenapp.

Also includes a manuscript, numbered 17a (37) which Thomson sets a problem for Ledermann, asking him in his letter if he can provide a proof.

Scope and Contents In the first letter, dated 13 Mar 1928 and numbered 17 (38), Thomson discusses the work of M S Bartlett, in particular that the assumptions he makes about each person's ability in the unknown quality e will average zero over a number of persons. He refers to specification equations, and his trouble with them, in particular that they are true for all persons, using Robinson Crusoe as an analogy to show the...

Scope and Contents

Thomson thanks Ledermann for his response to his previous letter, stating how neat his proofs are and discussing them at length. He refers to a paper of Aitken's published in the Edinburgh Mathematics Society, series 2, vol. 4, part II, and explores how the formula therein can assist them. The letter is unsigned, so appears to be incomplete.

Scope and Contents

Thomson asks Ledermann for a simple explanation of how Thurstone rotates the axis to the position of simple structure for use in The Factorial Analysis of Human Ability.

Scope and Contents

Thomson stresses that he does not wish Ledermann to reply to the letter while his Mother is visiting. He refers to a manuscript he sent Ledermann regarding the connection between estimation and selection, outlining a point he can add to it and referring to matrices of Aitken's.

He discusses orthogonal projection, estimation of regression, the selection formulae, and how these can be seen as one; as well as the division of factorial analysis after selection into two parts.