HOME COMPUTERS AND EDUCATIONAL OUTCOMES: EVIDENCE FROM THE NLSY97 and CPS*

Although computers are universal in the classroom, nearly 20 million children in the United States do not have computers in their homes. Surprisingly, only a few previous studies explore the role of home computers in the educational process. Home computers might be very useful for completing school assignments, but they might also represent a distraction for teenagers. We use several identification strategies and panel data from the two main U.S. data sets that include recent information on computer ownership among children—the 2000–2003 Current Population Survey (CPS) Computer and Internet Use Supplements matched to the CPS basic monthly files and the National Longitudinal Survey of Youth 1997 (NLSY97)—to explore the causal relationship between computer ownership and high school graduation and other educational outcomes. Teenagers who have access to home computers are 6–8 percentage points more likely to graduate from high school than teenagers who do not have home computers after controlling for individual, parental, and family characteristics. We generally find evidence of positive relationships between home computers and educational outcomes using several identification strategies, including controlling for typically unobservable home environment and extracurricular activities in the NLSY97, fixed effects models, instrumental variables, and including future computer ownership and falsification tests. Home computers may increase high school graduation by reducing nonproductive activities, such as truancy and crime, among children in addition to making it easier to complete school assignments (JEL I2).     

On the number of separable partitions

Consider partitions of a given set A of n distinct points in general position in ℝ ^d into parts where each pair of parts can be separated by a hyperplane that contains a given set of points E. We consider the problem of counting and generating all such partitions (correcting a classic 1967 result of Harding about the number of such partitions into two parts). Applications of the result to partition problems are presented.     

Hogging the road

This essay examines how aesthetic, corporate and cultural formations have radically altered. motorcycling and its image over the past two decades as a means to highlight more general changes in cultural politics, citizenship and governing through culture. The essay begins with the Guggenheim's The Art of the Motorcycle exhibit, treated. as a means for shaping and governing thought and conduct about and on motorcycles. The essay then addresses numerous articulations between aesthetic criteria and economic practices that have benefited. corporate and professional entities at the expense of long-time motorcyclists. Lastly, the essay formulates genealogical criteria for assessing attempts to represent culture in the hopes of more actively engaging in struggles over not just representation, but the activation of modes of thought, conduct and citizenship.     

On a nonparametric test for the mixed-model

Nonparametric tests for the null hypothesis of no treatment effect in the mixed-model experiment which involves n randomly chosen subjects who respond once to each of ρ distinct treatments have been developed by Koch and Sen (1968), These tests were based on the assumption of compound symmetry of the error vectors and on the weaker assumption of diagonal symmetry of the error vectors. This paper considers an alternative (permutationally) distribution-free test under this latter assumption. The new test follows the same type of distribution theory as those in Koch and Sen, but utilizes the inherent invariance structure in a more visable and direct way.     

The present status of confidence interval estimation on variance components in balanced and unbalanced random models

Much research has been conducted to develop confidence Intervals on linear combinations and ratios of variance components in balanced and unbalanced random models.This paper first presents confidence intervals on functions of variance components in balanced designs.These results assume that classical analysis of variance sums of squares are independent and have exact scaled chi-squared distributions.In unbalanced designs, either one or both of these assumptions are violated, and modifications to the balanced model intervals are required.We report results of some recent work that examines various modifications for some particular unbalanced designs.     

A simpler way of obtaining non-sIngularity conditions of rotatability

In response surface designs, it is not usually easy to handle the moment matrix X'X, especially for higher orders. This paper presents a method in which the moment matrix of a response surface of any order can be standardized, i.e., X'X splits into a diagonal matrix consisting of sub-matrices of lower order. This eases the calculation of the determinant and the inverse of X'X. The method has been illustrated with applications to second, third and fourth order response surfaces.     

The Beginnings of Tool Use by Infants and Toddlers

Children (aged 9, 14, 19, and 24 months) were encouraged to use tools to achieve a demonstrated goal. Each tool was most efficiently applied when held by the handle with the thumb toward the head of the tool in a radial grip. The tools were presented at midline and oriented to the left and right on alternating trials, so the children who managed to grasp a tool in both orientations with the radial grip demonstrated planning of actions in advance. The tools included a spoon, hairbrush, toy hammer, and magnet; the goals were to feed one's self, feed another, brush one's hair, brush another's hair, hit pegs, and retrieve metal objects. Children were found to use more radial grips with the self‐directed tools (i.e., hairbrush‐to‐self and spoon‐to‐self), indicating that they could plan their actions better when directed toward the self than toward an external goal.