Selecting significant effects in factorial designs: Lenth's method versus using negligible interactions

Among the many analytical techniques that have been published to analyze the significance of the effects in the absence of replications, two have emerged as the most widely used in text books as well as statistical software packages: The Lenth's method and the estimation of the variance of the effects from the values of those considered negligible. This article shows that neither is better than the other in all cases, and by analyzing the results obtained in a wide variety of situations it provides guidelines on when it is preferable to use one or the other technique.     

Selecting significant effects in factorial designs: Lenth’s method versus the Box-Meyer approach

The Lenth method is conceptually simple and probably the most common approach to analyzing the significance of the effects in factorial designs. Here, we compare it with a Bayesian approach proposed by Box and Meyer and which does not appear in the usual software packages. The comparison is made by simulating the results of 4, 8 and 16 run designs in a set of scenarios that mirror practical situations and analyzing the results provided by both methods. Although the results depend on the number of runs and the scenario considered, the use of the Box and Meyer method generally produces better results.     

Causes and Consequences of Block Share Purchases. Evidence from Spanish Non-Financial Firms

The structure of Spanish capital markets doesnot facilitate an efficient market forcorporate control through takeover process,which assumes that inefficient management isreplaced by competing teams. The ownershipstructure of listed companies is highlyconcentrated, with extremely low floating stockfor some companies. At the same time animportant number of companies have introducedanti-takeover provisions in their statutes.There is another way of disciplining managementthrough the exit solution: by transferring theownership of significant blocks of shares, amarket for partial corporate control, asalternative to the takeover market. Theobjective of this paper is to test empiricallythe causes and consequences of block purchasesin Spain for non-financial listed companies.The main results are: i) There is no evidencethat previous poor performance of the companiescauses block increases; ii) Block increasesoccur more frequently in companies with lowerownership concentration. After the blockincrease, on average, the ownership of thelargest shareholder increases. iii) After blockincreases there are significant board changes,for both executive board members and also fornon-executives. (iv) The transfer of blocksoccurs more frequently for smaller companies.We conclude that agency theory predictionsabout the disciplining role of partial takeoveractivity are not fully supported. They arecontingent on institutional characteristics ofthe corporate governance system.