Browsing by Subject "GOODNESS-OF-FIT"

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  • Zhoolideh Haghighi, Mohammad H.; Raouf, Mojtaba; Khosroshahi, Habib. G.; Farhang, Amin; Gozaliasl, Ghassem (2020)
    We characterize the relaxation state of galaxy systems by providing an assessment of the reliability of the photometric and spectroscopic probe via the semianalytic galaxy evolution model. We quantify the correlations between the dynamical age of simuglated galaxy groups and popular proxies of halo relaxation in observation, which are mainly either spectroscopic or photometric. We find the photometric indicators demonstrate a stronger correlation with the dynamical relaxation of galaxy groups compared to the spectroscopic probes. We take advantage of the Anderson Darling statistic (A(2)) and the velocity segregation (Delta V) as our spectroscopic indicators, and use the luminosity gap (Delta m(12)) and the luminosity decentering (D-offset) as photometric ones. First, we find that a combination of Delta m(12) and D-offset evaluated by a bivariant relation (B = 0.04 x Delta m(12) - 0.11 x Log(Doff-set) + 0.28) shows a good correlation with the dynamical age compared to all other indicators. Second, by using the observational X-ray surface brightness map, we show that the bivariant relation brings about some acceptable correlations with X-ray proxies. These correlations are as well as the correlations between A(2) and X-ray proxies, offering a reliable yet fast and economical method of quantifying the relaxation of galaxy systems. This study demonstrates that using photometric data to determine the relaxation status of a group will lead to some promising results that are comparable with the more expensive spectroscopic counterpart.
  • Lopez-Pedersen, Anita; Mononen, Riikka; Korhonen, Johan; Aunio, Pirjo; Melby-Lervåg, Monica (2021)
    This study investigated the psychometric properties of the Early Numeracy Screener. The Early Numeracy Screener is a teacher-administered, paper-and-pencil test measuring counting skills, numerical relational skills, and basic arithmetic skills. Three hundred and sixty-six first graders took the Early Numeracy Screener at the beginning of the school year. Confirmatory factor analysis was conducted in order to examine whether the screening tool was identified as a one-factor model or a three-factor model. The confirmatory factor analysis found evidence for the three-factor model, establishing construct validity. Evidence for criterion-related validity was found in crosstabulation and correlation with the national test measuring overall mathematics performance taken towards the end of the school year. The Early Numeracy Screener may serve as an indicator of young children's performance in early numeracy. The brevity and ease of use of the Early Numeracy Screener make it suitable for classroom instructional settings.