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 Title
 Conditional bootstrap methods for censored data.
 Creator

Kim, JiHyun., Florida State University
 Abstract/Description

We first consider the random censorship model of survival analysis. The pairs of positive random variables ($X\sb{i},Y\sb{i}$), i = 1,$\...$,n, are independent and identically distributed, with distribution functions F(t) = P($X\sb{i} \leq\ t$) and G(t) = P($Y\sb{i} \leq\ t$) and the Y's are independent of the X's. We observe only ($T\sb{i},\delta\sb{i}$), i = 1,$\...$,n, where $T\sb{i}$ = min($X\sb{i},Y\sb{i}$) and $\delta\sb{i}$ = I($X\sb{i} \leq\ Y\sb{i}$). The X's represent survival times...
Show moreWe first consider the random censorship model of survival analysis. The pairs of positive random variables ($X\sb{i},Y\sb{i}$), i = 1,$\...$,n, are independent and identically distributed, with distribution functions F(t) = P($X\sb{i} \leq\ t$) and G(t) = P($Y\sb{i} \leq\ t$) and the Y's are independent of the X's. We observe only ($T\sb{i},\delta\sb{i}$), i = 1,$\...$,n, where $T\sb{i}$ = min($X\sb{i},Y\sb{i}$) and $\delta\sb{i}$ = I($X\sb{i} \leq\ Y\sb{i}$). The X's represent survival times, the Y's represent censoring times. Efron (1981) proposed two bootstrap methods for the random censorship model and showed that they are distributionally the same. Akritas (1986) established the weak convergence of the bootstrapped KaplanMeier estimator of F when bootstrapping is done by this method. Let us now consider bootstrapping more closely. Suppose that we wish to estimate the variance of F(t). If we knew the Y's then we would condition on them by the ancillarity principle, since the distribution of the Y's does not depend on F. That is, we would want to estimate Var$\{$F(t)$\vert Y\sb1,\...,Y\sb{n}\}$. Unfortunately, in the random censorship model we do not see all the Y's. If $\delta\sb{i}$ = 0 we see the exact value of $Y\sb{i}$, but if $\delta\sb{i}$ = 1 we know only that $Y\sb{i} > T\sb{i}$. Let us denote this information on the Y's by ${\cal C}$. Thus, what we want to estimate is Var$\{$F(t)$\vert{\cal C}\}$. Efron's scheme is appropriate for estimating the unconditional variance. We propose a new bootstrap method which provides an estimate of Var$\{$F(t)$\vert{\cal C}\}$., In this research we show that the KaplanMeier estimator of F formed by the new bootstrap method has the same limiting distribution as the one by Efron's approach. The results of simulation studies assessing the small sample performance of the two bootstrap methods are reported. We also consider the model in which the $X\sb{i}$'s are censored by the $Y\sb{i}$'s and also by known fixed constants, and propose an appropriate bootstrap method for that model. This bootstrap method is a readily modified version of the new bootstrap method above.
Show less  Date Issued
 1990, 1990
 Identifier
 AAI9113938, 3162201, FSDT3162201, fsu:78399
 Format
 Document (PDF)
 Title
 Information and Culture: Cultural Differences in the Perception and Recall of Information from Advertisements.
 Creator

Kim, JiHyun, Gross, Melissa, Goldsmith, Ronald, Marty, Paul F., Lustria, Mia Liza A., School of Library and Information Studies, Florida State University
 Abstract/Description

Information in general is congruent with cultural values because a culture consists of transmitted social knowledge. Crosscultural research demonstrates that audiences who are fostered by different cultures may have different understandings of information. This research represents a comprehensive crosscultural study using an experimental method, and contributes to multicultural studies in understanding individuals' perceptions of information, recalls of information, and attitudes based on...
Show moreInformation in general is congruent with cultural values because a culture consists of transmitted social knowledge. Crosscultural research demonstrates that audiences who are fostered by different cultures may have different understandings of information. This research represents a comprehensive crosscultural study using an experimental method, and contributes to multicultural studies in understanding individuals' perceptions of information, recalls of information, and attitudes based on cultures. This study investigates whether people in individual or collective cultures have different perceptions of information in advertisements, recall of information in advertisements, and attitudes toward advertisements providing information in high or low context conditions. The theoretical frameworks of interest in the study are two cultural theories: Hofstede's (1980) individualism vs. collectivism and Hall's (1976) high context vs. low context. The hypotheses were tested using a 2 × 2 factorial betweensubject experimental design: individualism/collectivism and high context/low context. The lowcontext condition employed facts and direct information in a test advertisement, while the highcontext condition included indirect messages (e.g. images, moods, and symbols) in a test advertisement. The responses of experimental groups were compared and analyzed after they were exposed to two different stimuli. The subjects consisted of 82 American students and 82 Korean students. To check the two subject groups' cultural differences, this research employs Oyserman et al.'s (2002) individualism and collectivism scale. The test results indicate that American subjects are classified as an individualistic culture, while the Korean subjects represent a collectivistic culture. The experiment results indicate that students in individualistic and collectivistic cultures respond differently to information in high or lowcontext advertisements. Koreans tend to be more comfortable with highcontext culture that uses indirect and ambiguous messages. The Korean subjects showed higher ratings for perceptions of information in a highcontext advertisement than the American subjects. The American subjects perceived more information than Korean subjects in the lowcontext advertisement, but this result was not statistically significant. There is no statistically significant difference in recall of information from high and lowcontext conditions between American and Korean subjects. The American subjects showed significantly more favorable attitudes toward the lowcontext advertisement than the Korean students. However, there was no statistically significant difference in attitudes toward the highcontext advertisement between American and Korean students. This study partially supports the notion that cultural differences influence the perception of information in advertisements, recall of information in advertisements, and attitudes toward advertisements providing information in high or low context conditions. The findings obtained in this study suggest several exciting opportunities for future research.
Show less  Date Issued
 2012
 Identifier
 FSU_migr_etd4950
 Format
 Thesis