Chapter 2 - Database System Concepts and Architecture Data Models, Schemas and Instances A characteristic of the database approach is that it provides a level of data abstraction, by hiding details of data storage that are not needed by most users. A data model is a collection of concepts that can be used to describe the structure of a database. The model provides the necessary means to achieve the abstraction. The structure of a database is characterized by data types, relationships
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usually impractical and unnecessary to measure all the elements in the population of interest. The are two main types of sampling procedures suitable for conducting educational research, which is probability also known as random sampling and non-probability or non-random sampling. This paper will further discuss the two categories of sampling procedures that are commonly used in educational research and highlight the strength and weakness of using the discussed sampling procedures. Probability sampling
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Journal of Information Systems Vol. 16, No. 2 Fall 2002 pp. 209–222 Impact of Information Technology on Public Accounting Firm Productivity Rajiv D. Banker Hsihui Chang The University of Texas at Dallas Yi-ching Kao University of Wisconsin–Milwaukee ABSTRACT: In recent years, information technology (IT) has played a critical role in the services provided by the public accounting industry. However, no empirical research has evaluated the impact of IT on public accounting firms. This
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Q U A N T I T A T I V E F I N A N C E V O L U M E 2 (2002) 45–60 INSTITUTE O F PHYSICS PUBLISHING RE S E A R C H PA P E R quant.iop.org Dynamics of implied volatility surfaces Rama Cont1,3 and Jos´ da Fonseca2 e Centre de Math´ matiques Appliqu´ es, Ecole Polytechnique, F-91128 e e Palaiseau, France 2 Ecole Superieure d’Ingenierie Leonard de Vinci, F-92916 Paris La D´ fense, e France E-mail: Rama.Cont@polytechnique.fr and jose.da fonseca@devinci.fr Received 20 September 2001 Published 4
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Parameter Statistic 3 If X1, . . . , Xn are independent random variables having a common distribution F, g , then we say that they constitute a sample (sometimes called a random sample) from the distribution F. 4 2 10/24/2011 Parametric inference problem: Problems in which the form of the underlying distribution is specified up to a set of unknown parameters, eg: Nonparametric inference problem: problems in hi h i which nothing is assumed about the form thi i d b t th f of F ◦
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Non parametric (Chi square distribution) Suppose that there is interest in testing if there is any relationship between the scholastic achievement (final grade point average in college) of a business administration graduate and his or her level of income. The null hypothesis is: there is no relationship between scholastic achievement and the level of income, H1 states that there is a relationship. For this test, the 0.01 level of significance was selected. It was decided to classify the scholastic
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QUADLEC – Quiz 1 formula sheet PARAMETRIC TESTS: |SIGN TEST |SIGNED RANK TEST | |- tests [pic] or [pic] |- tests : | |- C.R. if x < [pic], P(X [pic], P(X>x when p=½) < α |[pic]
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described. These models, in order to apply interval estimation and hypothesis testing parameters Also described, including the next two sample cases, when the purpose of comparing two or more of the population For their means and variances. Secondly, non-parametric inference tests are also described in the case where the data Sample distribution is not compatible with standard parameter distribution. Thirdly, using multiple resampling methods Computer -generated random sample finally introduced the characteristics
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Journal of Information Systems Vol. 16, No. 2 Fall 2002 pp. 209–222 Impact of Information Technology on Public Accounting Firm Productivity Rajiv D. Banker Hsihui Chang The University of Texas at Dallas Yi-ching Kao University of Wisconsin–Milwaukee ABSTRACT: In recent years, information technology (IT) has played a critical role in the services provided by the public accounting industry. However, no empirical research has evaluated the impact of IT on public accounting firms. This study focuses
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ii) A pared T-Test may be recommended. iii) The samples are normal, related and are with equal variance. iv) If the variances are not equal conduct the same test without taking variance as equal. If the two samples are not normal, then a non-parametric willcoxon test may be carried out. v) The p-value is greater than the level of significance. 0.82 > 0.05 Hence we cannot reject Ho. The rate of production of workers per hour has not improved by introducing the Viskam’s method. b) Standard
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