Pure announcement and time effects in the dividend-discount model

AbstractThe before-and-after study with multiple unaffected control groups is widely applied to study treatment effects. The current methods usually assume that the control groups’ differences between the before and after periods, i.e. the group time effects, follow a normal distribution. However, there is usually no strong a priori evidence for the normality assumption, and there are not enough control groups to check the assumption. We propose to use a flexible skew-t distribution family to model group time effects, and consider a range of plausible skew-t distributions. Based on the skew-t distribution assumption, we propose a robust-t method to guarantee nominal significance level under a wide range of skew-t distributions, and hence make the inference robust to misspecification of the distribution of group time effects. We also propose a two-stage approach, which has lower power compared to the robust-t method, but provides an opportunity to conduct sensitivity analysis. Hence, the overall method of analysis is to use the robust-t method to test for the overall hypothesized range of shapes of group variation; if the test fails to reject, use the two-stage method to conduct a sensitivity analysis to see if there is a subset of group variation parameters for which we can be confident that there is a treatment effect. We apply the proposed methods to two datasets. One dataset is from the Current Population Survey (CPS) to study the impact of the Mariel Boatlift on Miami unemployment rates between 1979 and 1982.The other dataset contains the student enrollment and grade repeating data in West Germany in the 1960s with which we study the impact of the short school year in 1966–1967 on grade repeating rates.

Download Full-text

Predicted harvest time effects on switchgrass moisture content, nutrient concentration, yield, and profitability

Biomass and Bioenergy ◽

10.1016/j.biombioe.2017.09.017 ◽

2018 ◽

Vol 108 ◽

pp. 74-89 ◽

Cited By ~ 4

Author(s):

Karen R. Lindsay ◽

Michael P. Popp ◽

Charles P. West ◽

Amanda J. Ashworth ◽

Alexandre Caldeira Rocateli ◽

...

Keyword(s):

Moisture Content ◽

Nutrient Concentration ◽

Harvest Time ◽

Time Effects

Download Full-text

Can Pre-Service Biology Teachers’ Professional Knowledge and Diagnostic Activities Be Fostered by Self-Directed Knowledge Acquisition via Texts?

Education Sciences ◽

10.3390/educsci11050244 ◽

2021 ◽

Vol 11 (5) ◽

pp. 244

Author(s):

Maria Kramer ◽

Christian Förtsch ◽

Birgit J. Neuhaus

Keyword(s):

Knowledge Acquisition ◽

Scientific Reasoning ◽

Assessment Tool ◽

Instructional Quality ◽

Professional Knowledge ◽

Biology Teachers ◽

Time Effects ◽

Effect Of Treatment ◽

Scientific Reasoning Skills ◽

Design Paper

In a diagnostic context of reasoning about instructional quality, scientific reasoning skills can be described as diagnostic activities, which require professional knowledge. Different approaches to enhance pre-service teachers’ professional knowledge (PCK, CK, PK), as well as diagnostic activities exist. However, results about their effectiveness are still inconsistent. We systematically investigated the effectiveness of self-directed knowledge acquisition via texts on PCK, CK, PK, and diagnostic activities of 81 pre-service biology teachers following an experimental design. Paper-pencil tests, measuring PCK, CK, and PK, and the video-based assessment tool DiKoBi Assess, measuring diagnostic activities in the context of diagnosing instructional quality, were used pre and post an intervention. Intervention included four treatments on self-directed knowledge acquisition via texts on (1) PCK, (2) CK, (3) PK, (4) combination PCK/CK/PK. Treatment (5) served as control. Mixed ANOVAs showed large time effects for PCK and CK, but no interaction effect concerning knowledge facets between time and treatment for any of the treatments. Time effects might be due to pre-service teachers’ scientific reasoning on biology instruction that activated knowledge. An ANCOVA showed no significant effect of treatment on diagnostic activities either. We conclude that scientific reasoning about instructional quality is more effective for knowledge acquisition than text-work.

Download Full-text