Subjective measurements of persistence of time series
- Authors: Poswayo, Sihle
- Date: 2018
- Subjects: Time-series analysis , Space and time Time -- Philosophy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34372 , vital:33361
- Description: In this paper we suggest the use of subjective judgements to measure persistence in time series by comparing pairs of graphs with different Hurst exponents. The group of respondents consisted of 40 volunteers who were asked to identify the more jagged out of two graphs presented to them (that is, less persistent). The respondents were approached as a group and requested to work independently in the completion of ques- tionnaires administered to them. The respondents were supervised by the researchers. The graphs were simulated using time series package of Mathematica R [26]. The re- sponses were processed using an algorithm based on the Thurstone-Mosteller model for paired comparisons [29]. The results of the analysis show that the human eye is capable of distinguishing graphs of time series with Hurst exponent difference as small as only 0.02.
- Full Text:
- Date Issued: 2018
- Authors: Poswayo, Sihle
- Date: 2018
- Subjects: Time-series analysis , Space and time Time -- Philosophy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34372 , vital:33361
- Description: In this paper we suggest the use of subjective judgements to measure persistence in time series by comparing pairs of graphs with different Hurst exponents. The group of respondents consisted of 40 volunteers who were asked to identify the more jagged out of two graphs presented to them (that is, less persistent). The respondents were approached as a group and requested to work independently in the completion of ques- tionnaires administered to them. The respondents were supervised by the researchers. The graphs were simulated using time series package of Mathematica R [26]. The re- sponses were processed using an algorithm based on the Thurstone-Mosteller model for paired comparisons [29]. The results of the analysis show that the human eye is capable of distinguishing graphs of time series with Hurst exponent difference as small as only 0.02.
- Full Text:
- Date Issued: 2018
Good's casualty for time series: a regime-switching framework
- Authors: Mlambo, Farai Fredric
- Date: 2014
- Subjects: Time-series analysis , Econometrics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/6018 , vital:21025
- Description: Causal analysis is a significant role-playing field in the applied sciences such as statistics, econometrics, and technometrics. Particularly, probability-raising models have warranted significant research interest. Most of the discussions in this area are philosophical in nature. Contemporarily, the econometric causality theory, developed by C.J.W. Granger, is popular in practical, time series causal applications. While this type of causality technique has many strong features, it has serious limitations. The processes studied, in particular, should be stationary and causal relationships are restricted to be linear. However, we cannot classify regime-switching processes as linear and stationary. I.J. Good proposed a probabilistic, event-type explication of causality that circumvents some of the limitations of Granger’s methodology. This work uses the probability raising causality ideology, as postulated by Good, to propose some causal analysis methodology applicable in a stochastic, non-stationary domain. There is a proposal made for a Good’s causality test, by transforming the originally specified probabilistic causality theory from random events to a stochastic, regime-switching framework. The researcher performed methodological validation via causality simulations for a Markov, regime-switching model. The proposed test can be used to detect whether none stochastic process is causal to the observed behaviour of another, probabilistically. In particular, the regime-switch causality explication proposed herein is pivotal to the results articulated. This research also examines the power of the proposed test by using simulations, and outlines some steps that one may take in using the test in a practical setting.
- Full Text:
- Date Issued: 2014
- Authors: Mlambo, Farai Fredric
- Date: 2014
- Subjects: Time-series analysis , Econometrics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/6018 , vital:21025
- Description: Causal analysis is a significant role-playing field in the applied sciences such as statistics, econometrics, and technometrics. Particularly, probability-raising models have warranted significant research interest. Most of the discussions in this area are philosophical in nature. Contemporarily, the econometric causality theory, developed by C.J.W. Granger, is popular in practical, time series causal applications. While this type of causality technique has many strong features, it has serious limitations. The processes studied, in particular, should be stationary and causal relationships are restricted to be linear. However, we cannot classify regime-switching processes as linear and stationary. I.J. Good proposed a probabilistic, event-type explication of causality that circumvents some of the limitations of Granger’s methodology. This work uses the probability raising causality ideology, as postulated by Good, to propose some causal analysis methodology applicable in a stochastic, non-stationary domain. There is a proposal made for a Good’s causality test, by transforming the originally specified probabilistic causality theory from random events to a stochastic, regime-switching framework. The researcher performed methodological validation via causality simulations for a Markov, regime-switching model. The proposed test can be used to detect whether none stochastic process is causal to the observed behaviour of another, probabilistically. In particular, the regime-switch causality explication proposed herein is pivotal to the results articulated. This research also examines the power of the proposed test by using simulations, and outlines some steps that one may take in using the test in a practical setting.
- Full Text:
- Date Issued: 2014
An analysis of neural networks and time series techniques for demand forecasting
- Authors: Winn, David
- Date: 2007
- Subjects: Time-series analysis , Neural networks (Computer science) , Artificial intelligence , Marketing -- Management , Marketing -- Data processing , Marketing -- Statistical methods , Consumer behaviour
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:5572 , http://hdl.handle.net/10962/d1004362 , Time-series analysis , Neural networks (Computer science) , Artificial intelligence , Marketing -- Management , Marketing -- Data processing , Marketing -- Statistical methods , Consumer behaviour
- Description: This research examines the plausibility of developing demand forecasting techniques which are consistently and accurately able to predict demand. Time Series Techniques and Artificial Neural Networks are both investigated. Deodorant sales in South Africa are specifically studied in this thesis. Marketing techniques which are used to influence consumer buyer behaviour are considered, and these factors are integrated into the forecasting models wherever possible. The results of this research suggest that Artificial Neural Networks can be developed which consistently outperform industry forecasting targets as well as Time Series forecasts, suggesting that producers could reduce costs by adopting this more effective method.
- Full Text:
- Date Issued: 2007
- Authors: Winn, David
- Date: 2007
- Subjects: Time-series analysis , Neural networks (Computer science) , Artificial intelligence , Marketing -- Management , Marketing -- Data processing , Marketing -- Statistical methods , Consumer behaviour
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:5572 , http://hdl.handle.net/10962/d1004362 , Time-series analysis , Neural networks (Computer science) , Artificial intelligence , Marketing -- Management , Marketing -- Data processing , Marketing -- Statistical methods , Consumer behaviour
- Description: This research examines the plausibility of developing demand forecasting techniques which are consistently and accurately able to predict demand. Time Series Techniques and Artificial Neural Networks are both investigated. Deodorant sales in South Africa are specifically studied in this thesis. Marketing techniques which are used to influence consumer buyer behaviour are considered, and these factors are integrated into the forecasting models wherever possible. The results of this research suggest that Artificial Neural Networks can be developed which consistently outperform industry forecasting targets as well as Time Series forecasts, suggesting that producers could reduce costs by adopting this more effective method.
- Full Text:
- Date Issued: 2007
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