In studying natural history of a disease, incident studies provide the best quality estimates; in contrast, prevalent studies introduce a sampling bias, which, if the onset time of the disease follows a stationary Poisson process, is called length bias. When both types of data are available, combining the samples under the assumption that failure times in incident and prevalent cohorts come from the same distribution function, could improve the estimation process from a revalent sample. We verify this assumption using a Smirnov type of test and construct a likelihood function from a combined sample to parametrically estimate the survival through maximum likelihood approach. Finally, we use Accelerated Failure Time models to compare the effect of covariates on survival in incident, prevalent, and combined populations. Properties of the proposed test and the combined estimator are assessed using simulations, and illustrated with data from the Canadian Study of Health and Aging.

Thesis advisor: Robert Murphy / We empirically examine the Biased Expectations Hypothesis, which states that recent price movements in certain sectors play special roles in the formation of in- dividuals inflation expectations. Specifically we analyze whether economists rationally bias their expectations and whether economists and consumers naively bias their ex- pectations with respect to recent inflation in the food and energy sectors. We develop theoretical models for both rationally formed and naively formed inflation expecta- tions. We find that economists do not bias their rationally formed expectations and that consumers and economists do not naively form inflation expectations. Our results do not support the Biased Expectations Hypothesis; rather, they reinforce the use of core measures of inflation in policy making. / Thesis (BA) — Boston College, 2013. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Economics Honors Program. / Discipline: Economics.

We show how using censored regressors leads to expansion bias, or estimated effects that are proportionally too large. We show the necessity of this effect in bivariate regression and illustrate the bias using results for normal regressors. We study the bias when there is a censored regressor among many regressors, and we note how censoring can work to undo errors-in-variables bias. We discuss several approaches to correcting expansion bias. We illustrate the concepts by considering how censored regressors can arise in the analysis of wealth effects on consumption, and on peer effects in productivity.

Psychometricians and test developers use DIF analysis to determine if there is possible bias in a given test item. This study examines the conditions under which two predominant methods for determining differential item function compare with each other in item bias detection using an effect size statistic as the basis for comparison. The main focus of the present research was to test whether or not incorporating an effect size for LR DIF will more accurately detect DIF and to compare the utility of an effect size index across MH DIF and LR DIF methods. A simulation study was used to compare the accuracy of MH DIF and LR DIF methods using a p value or supplemented with an effect size. Effect sizes were found to increase the accuracy of DIF and the possibility of the detection of DIF across varying ability distributions, population distributions, and sample size combinations. Varying ability distributions and sample size combinations affected the detection of DIF, while population distributions did not seem to affect the detection of DIF.

In studying natural history of a disease, incident studies provide the best quality estimates; in contrast, prevalent studies introduce a sampling bias, which, if the onset time of the disease follows a stationary Poisson process, is called length bias. When both types of data are available, combining the samples under the assumption that failure times in incident and prevalent cohorts come from the same distribution function, could improve the estimation process from a revalent sample. We verify this assumption using a Smirnov type of test and construct a likelihood function from a combined sample to parametrically estimate the survival through maximum likelihood approach. Finally, we use Accelerated Failure Time models to compare the effect of covariates on survival in incident, prevalent, and combined populations. Properties of the proposed test and the combined estimator are assessed using simulations, and illustrated with data from the Canadian Study of Health and Aging.

The present monograph deals with the problem of sex differences in test results from various angles. Initially, the aim was to investigate whether the use of test results in selection could be considered fair in spite of sex differences in test score averages. As work progressed, the aim was specified towards clarifying in what manner test item content is related to sex differences in results and whether the observed differences are consistent over different groupé of men and women. After a brief review of some research results on sex differences in cognitive abilities, the Swedish Scholastic Aptitude Test (SSAT) is described. The SSAT is the measuring instrument in the following empirical studies. In chapter four there is a survey of a number of models which aim at correcting for unfair group differences in test scores when the tests are to be used in selection. Two models are examined empirically. In chapter five such models are examined that aim to identify individual test items giving deviant results. The conclusion of these two studies is that statistical models can not solve the problem of group differences in test scores, since what constitutes fairness is mainly a value problem. This cannot be dealt with in a strictly technical manner. Chapter six is devoted to analyses of test item content and sex differences in all subtests on vocabulary and general knowledge which have been used in the SSAT between 1977 and 1983. The conclusion from these analyses is that test item content seems to determine whether men or women obtain higher test scores. Some subcategories of items seem to favour men and others favour women. The extent to which the testees are able to predict which items favour one sex or the other is studied in chapter seven. The testees could only make appropriate judgements to a very limited extent. In chapter eight the significance of age and education for sex differences in test scores is studied. Furthermore, sex differences on individual items are studied for men and women having the same score on the subtest level. Sex differences in scores on individual test items could not be eliminated by equalizing age, education or subtest achievement respectively. Finally, the results from all the studies are summarized and discussed in view of their significance for the validity of the tests. / digitalisering@umu

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Work by Blanchard-Fields has consistently found that older adults are prone to making dispositional inferences in certain contexts (Blanchard-Fields, 1994; 1996; 1999); however mechanisms underlying these tendencies have yet to be explored. The present study assessed the influence that personal belief has on attitude attributions made by both young and older adults. Using the attitude-attribution paradigm, participants made judgments about a targets actual attitude based on an essay that was written by the target. The essay contained a position on a controversial social issue, i.e. prayer in public school, that the target was instructed to advocate. Replicating past research, older adults rated the targets attitude to be more strongly consistent with the content of the essay than young adults did. Personal beliefs did not have a large effect on attitude attributions, however age and belief related differences appeared in both confidence ratings and as a function of attributional complexity. Fluid reasoning was also found to have an impact on attributions.

Recent theory predicts that two factors influencing the CEO’s view of risk, overconfidence and debt-like compensation, have implications for CEO forced turnover and firm equity value, respectively. We test each of these predictions using large samples of CEOs from S and P 1500 firms, with statistical methods such as Cox proportional semi-parametric hazard models and Ordinary Least Squares regressions. Section 2 tests the theoretical prediction that CEOs with excessively low or excessively high overconfidence face a higher likelihood of forced turnover. We find empirical support for this prediction: excessively overconfident (diffident) CEOs have forced turnover hazard rates approximately 67 percent (97 percent) higher than moderately overconfident CEOs. To the extent that boards terminate non-value-maximizing CEOs, the results are broadly consistent with the view that there is an interior optimum level of managerial overconfidence that maximizes firm value. Section 3 tests the theoretical prediction that debt or debt-like compensation can be used as a part of optimal executive compensation, leading to an increase in the value of equity. We find weak evidence of positive abnormal returns in response to decreases in the deviation from optimal CEO debt-to-equity when the CEO’s debt-to-equity was less than the firm’s or when then firm had low institutional ownership. The results suggest that the optimal use of debt compensation can in fact be beneficial to equity holders.

In school, all children at some time have been disruptive; however, there are a select few who are continually disruptive and identified by school personnel as those who may have a disruptive behavior disorder such as ADHD. Many times these children are boys and of a minority group (Root & Resnick, 2003). Information collected from school teachers and parents most often provides the basis for diagnosing ADHD, whether reliable or objective. The purpose of the study was to investigate any differences in the way in which teachers respond to behavioral difficulties associated with ADHD for African American girls and boys as compared to White girls and boys, with control for SES and perceived school climate as potential confounds. These results are promising in that teachers’ responses suggest similarity in perceptions of children’s behavior regardless of children’s socioeconomic status, gender and ethnicity. The results indicated that a significant difference exists in that teachers would talk to the counselor about the child’s behavior based on the child’s ethnicity, gender, and SES. When controlling for school climate, there was a significant difference in teacher responses to unusualness of inattention, which indicated that the better the school climate, the more unusual the inattention was perceived. Also, results indicated that the teacher’s ethnicity and/or ethnicity and gender affected how they perceived the child’s behavior.