<abstract xmlns="http://www.w3.org/1999/xhtml"><p>The quadratic trend is a statistical model described by the quadratic function. Finding its extremum (also called the vertex or the turning point) using differential calculus or completing the square method is very well known in the literature. In this paper, a new method for finding the extremum of the quadratic function, based on a simple mathematical inequality is proposed. In comparison with the other two known methods, our method does not require the differentiability assumption and it takes fewer steps than completing the square method. Also, it is shown how the turning point for the quadratic trend can be applied in forecasting the unemployment rate in Croatia in the first quarter of 2019. The obtained conclusions are equal to the conclusions obtained in the usual way by using forecasting software.</p></abstract>

The quadratic trend is a statistical model described by the quadratic function. Finding its extremum (also called the vertex or the turning point) using differential calculus or completing the square method is very well known in the literature. In this paper, a new method for finding the extremum of the quadratic function, based on a simple mathematical inequality is proposed. In comparison with the other two known methods, our method does not require the differentiability assumption and it takes fewer steps than completing the square method. Also, it is shown how the turning point for the quadratic trend can be applied in forecasting the unemployment rate in Croatia in the first quarter of 2019. The obtained conclusions are equal to the conclusions obtained in the usual way by using forecasting software.

A note on the turning point for the quadratic trend

Croatian Review of Economic, Business and Social Statistics

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

{"article-title":"A note on the turning point for the quadratic trend"}

The quadratic trend is a statistical model described by the quadratic function. Finding its extremum (also called the vertex or the turning point) using...

A note on the turning point for the quadratic trend

Published Online: Dec 21, 2019

Page range: 39 - 48

Received: Sep 29, 2019

Accepted: Nov 24, 2019

DOI: https://doi.org/10.2478/crebss-2019-0010

Keywords
forecasting unemployment rate, mathematical inequality, quadratic trend, single-variable quadratic function, turning point (vertex)

© 2019 Vedran Kojić et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

A note on the turning point for the quadratic trend

Published Online: Dec 21, 2019

Page range: 39 - 48

Received: Sep 29, 2019

Accepted: Nov 24, 2019

DOI: https://doi.org/10.2478/crebss-2019-0010

Keywordsforecasting unemployment rate, mathematical inequality, quadratic trend, single-variable quadratic function, turning point (vertex)

© 2019 Vedran Kojić et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
forecasting unemployment rate, mathematical inequality, quadratic trend, single-variable quadratic function, turning point (vertex)