Multiple window discrete scan statistic for higher-order Markovian sequences

Accurate and efficient methods to detect unusual clusters of abnormal activity are needed in many fields such as medicine and business. Often the size of clusters is unknown; hence, multiple (variable) window scan statistics are used to identify clusters using a set of different potential cluster sizes. We give an efficient method to compute the exact distribution of multiple window discrete scan statistics for higher-order, multi-state Markovian sequences. We define a Markov chain to efficiently keep track of probabilities needed to compute p-values for the statistic. The state space of the Markov chain is set up by a criterion developed to identify strings that are associated with observing the specified values of the statistic. Using our algorithm, we identify cases where the available approximations do not perform well. We demonstrate our methods by detecting unusual clusters of made free throw shots by National Basketball Association players during the 2009–2010 regular season.     

Body image, body satisfaction, and unsafe anal intercourse among men who have sex with men

Using survey results from the 1998 Twin Cities Lesbian, Gay, Bisexual, and Transgender (LGBT) Pride Festival (N = 535), we explored associations between body image and unsafe anal intercourse (UAI) among men who have sex with men (MSM), and evaluated whether body satisfaction mediated this association. MSM who reported underweight body image had lower odds than those who reported average weight of UAI (AOR = 0.33; 95% CI = 0.13, 0.85); body satisfaction was not found to mediate this association. 13.3% of men who reported overweight/obese body image had engaged in UAI compared with 21.6% of those who reported average weight and 8.2% of those who reported underweight (p < .05). Compared with MSM in exclusive relationships, MSM in non exclusive relationships had increased odds of UAI (AOR = 5.78; 95% CI = 2.96, 11.29) as did men who were not partnered (AOR = 3.20; 95% CI = 1.72, 5.93). These findings highlight the importance of including body image in sexual behavior models of MSM to better understand body image's role in influencing sexual risk and sexually transmitted infections (STI)/human immunodeficiency virus (HIV) transmission.     

The intersection of race, poverty and risk: understanding the decision to provide services to clients and to remove children

Studies have found that certain racial groups, particularly the children of African American families, are placed in foster care at a higher rate than children of other races. These families are also sometimes found to be afforded fewer services that might prevent these removals, relative to families of other races. It is unclear why this is so. Poverty has been suspected, and sometimes found, to be the primary cause of the disparity. Lacking in some of these analyses, however, was how risk of future abuse/neglect to the child entered into the decisions and particularly, how assumptions about race, poverty, and risk are factored into the decision-making process. It is important to understand this process if we are to find a way to correct it. The current study addresses this process.     

Motivational signage increases physical activity on a college campus

OBJECTIVE: The authors evaluated whether motivational signage influenced rates of stair use relative to elevator use on a college campus. PARTICIPANTS: In March and April 2004, the authors observed students, faculty, staff, and any visitors accessing a college campus building. METHODS: During Phase I, the authors monitored ascending stair and elevator use at the same time each weekday (Monday-Friday). During Phase II, the authors placed motivational signs encouraging stair use at the bottom of the stairs and outside and inside the elevators. During the third week (Phase III), the authors removed the signs. RESULTS: The authors observed 18,389 ascending trips during the 3 weeks of the study. Motivational signs significantly contributed to an 18.6% increase in stair use in the second week, which was maintained in the following week. CONCLUSIONS: The signage intervention successfully enhanced physical activity on a college campus by providing educational health tips that may have served as motivation to choose the stairs.     

Effect of certified personal trainer services on stage of exercise behavior and exercise mediators in female college students

OBJECTIVE: The authors examined the effect of certified personal trainer services on exercise behavior by using the transtheoretical model of behavioral change. PARTICIPANTS: Female college students (n = 449) completed surveys during the first week (T1) and last week (T2) of the fall semester. METHODS: Students receiving personal trainer services during the fall semester (experimental group, n = 31) were cross-matched with students who had not received services (control group, n = 31). RESULTS: The control group demonstrated a statistically significant regression in stage of exercise change scores; the experimental group did not. The authors found the 2 groups to have a statistically significant difference in the pattern of exercise behavior change over the course of the semester, with more active maintainers and progressors in the experimental group. CONCLUSIONS: Cognitive and behavioral processes of change, decisional balance, and scheduling self-efficacy significantly decreased in the control group, whereas cognitive processes of change, decisional balance, and scheduling self-efficacy remained statistically unchanged in the experimental group.     

Individuals' beliefs about the etiology of same-sex sexual orientation

We examined the relationships between beliefs about the etiology of having a same-sex sexual orientation, sexual prejudice, and support for gay-relevant legislation using the justification-suppression model of prejudice as our theoretical foundation. Results indicated that more belief that a same-sex sexual orientation was due to nurture factors predicted less support for gay-relevant legislation, and that this relationship was mediated by levels of sexual prejudice. The opposite pattern was found for belief that a same-sex sexual orientation was due to nature factors. This suggests that beliefs about the etiology of sexual orientation may serve as justification (or suppression) factors in the expression of prejudice toward gay men and lesbians.     

The effects of death reminders on sex differences in prejudice toward gay men and lesbians

Terror management research shows that death reminders (mortality salience) increase prejudice toward worldview violators. Two studies investigated whether death reminders exacerbated differences in heterosexual men's and women's reports of sexual prejudice (negative attitudes based on sexual orientation). Results showed that following death reminders, sex differences in anti-gay discrimination and affective prejudice toward gay men (but not toward lesbians) were larger, and that these increased sex differences were mediated by gender role beliefs. The current studies suggest that researchers may attenuate the effects of death reminders by lessening the perceived worldview violation in addition to alleviating the existential terror of death.     

Consistent Moment Selection Procedures for Generalized Method of Moments Estimation

This paper considers a generalized method of moments (GMM) estimation problem in which one has a vector of moment conditions, some of which are correct and some incorrect. The paper introduces several procedures for consistently selecting the correct moment conditions. The procedures also can consistently determine whether there is a sufficient number of correct moment conditions to identify the unknown parameters of interest. The paper specifies moment selection criteria that are GMM analogues of the widely used BIC and AIC model selection criteria. (The latter is not consistent.) The paper also considers downward and upward testing procedures. All of the moment selection procedures discussed in this paper are based on the minimized values of the GMM criterion function for different vectors of moment conditions. The procedures are applicable in time-series and cross-sectional contexts. Application of the results of the paper to instrumental variables estimation problems yields consistent procedures for selecting instrumental variables.     

Self-affine time series: measures of weak and strong persistence

In this paper, we examine self-affine time series and their persistence. Time series are defined to be self-affine if their power-spectral density scales as a power of their frequency. Persistence can be classified in terms of range, short or long range, and in terms of strength, weak or strong. Self-affine time series are scale-invariant, thus they always exhibit long-range persistence. Synthetic self-affine time series are generated using the Fourier power-spectral method. We generate fractional Gaussian noises (fGns), −1β1, where β is the power-spectral exponent. These are summed to give fractional Brownian motions (fBms), 1β3, where the series are self-affine fractals with fractal dimension 1D2; β=2 is a Brownian motion. With β>1, the time series are non-stationary and moments of the time series depend upon its length; with β<1 the time series are stationary. We define self-affine time series with β>1 to have strong persistence and with β<1 to have weak persistence. We use a variety of techniques to quantify the strength of persistence of synthetic self-affine time series with −3β5. These techniques are effective in the following ranges: (1) semivariograms, 1β3, (2) rescaled-range (R/S) analyses, −1β1, (3) Fourier spectral techniques, all values of β, and (4) wavelet variance analyses, all values of β. Wavelet variance analyses lack many of the inherent problems that are found in Fourier power-spectral analysis.