An Analysis of Sample Attrition in Panel Data: The Michigan Panel Study of Income Dynamics

By 1989 the Michigan Panel Study on Income Dynamics (PSID) had experienced approximately 50 percent sample loss from cumulative attrition from its initial 1968 membership. We study the effect of this attrition on the unconditional distributions of several socioeconomic variables and on the estimates of several sets of regression coefficients. We provide a statistical framework for conducting tests for attrition bias that draws a sharp distinction between selection on unobservables and on observables and that shows that weighted least squares can generate consistent parameter estimates when selection is based on observables, even when they are endogenous. Our empirical analysis shows that attrition is highly selective and is concentrated among lower socioeconomic status individuals. We also show that attrition is concentrated among those with more unstable earnings, marriage, and migration histories. Nevertheless, we find that these variables explain very little of the attrition in the sample, and that the selection that occurs is moderated by regression-to-the-mean effects from selection on transitory components that fade over time. Consequently, despite the large amount of attrition, we find no strong evidence that attrition has seriously distorted the representativeness of the PSID through 1989, and considerable evidence that its cross-sectional representativeness has remained roughly intact.

A Comparison of Intrauterine and Cervical Artificial Insemination Rods on Farrowing Rate and Litter Size in Artificially Mated Sows

This experiment compared the effects of two artificial insemination (AI) rods on farrowing rate and number of piglets born per litter. Three hundred eighty-nine sows were allotted into two experimental groups based on parity, body condition, and breed of sire influence of the sows. One hundred ninety-three matings were performed using the experimental intrauterine rod, and one hundred ninety-six matings were performed using the traditional cervical rod as the control. Total number of piglets born per litter was measured after each sow farrowed, and the farrowing rates were calculated at the end of the study. Farrowing rates were 68% and 66% and total number of piglets born per litter was 9.39 ± 0.55 and 9.74±0.53 for the experimental and control groups. Number of piglets born alive per litter was slightly lower than the total number of piglets born per litter for both groups, 8.97±0.54 and 9.29 ±0.52. The total number of piglets born per litter and the farrowing rates were not significantly (P \u3e 0.05) different between the experimental and control groups. Results from this trial produced no incentive to use the intrauterine AI rod in this or other similar commercial settings

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Master of Fine Arts (MFA)Art and DesignUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/156111/1/DeepBlue_Fitzgerald_2018_MFA_Thesis.pd

A Characterization of Primitive Polynomials over Finite Fields

AbstractWe characterize primitive polynomials, among irreducible polynomials, by the number of terms in a certain quotient. We apply this to BCH codes of maximal designed distance

Octonions

We present the basic properties of the octonions and construct the five exceptional simple Lie algebras

Invariants of Trace Forms over Finite Fields of Characteristic 2

AbstractLet K be a finite extension of F2. We compute the invariants of the quadratic form Q(x)=trK/F2(x(x2a+x2b)) and so determine the number of zeros in K. This is applied to finding the cross-correlation of certain binary sequences

Highly Degenerate Quadratic Forms over Finite Fields of Characteristic 2

Let K/F be an extension of finite fields of characteristic two. We consider quadratic forms written as the trace of xR(x), where R(x) is a linearized polynomial. We show all quadratic forms can be so written, in an essentially unique way. We classify those R, with coefficients 0 or 1, where the form has a codimension 2 radical. This is applied to maximal Artin-Schreier curves and factorizations of linearized polynomials

Norm Euclidean Quaternionic Orders

We determine the norm Euclidean orders in a positive definite quaternion algebra over Q

Norms of Sums of Squares

For a finite separable extension K/F of fields of characteristic not 2, the norm of a sum of 2n squares in K is a sum of 2n squares in F. We find explicit identities