Department of Mathematics, Informatics and Physics, Faculty of Economics, Agricultural University, 4000 Plovdiv, Bulgaria
(Manuscript received 9 April 2018; accepted for publication 23 May 2018)
Аbstract. The present study examines the yields of the following essential-oil crops: oil-yielding rose (Rosa Damascena), peppermint (Mentha piperita), lavender (Lavendula angustifolia Mill.), coriander (Coriandrum sativum L.) and lemon balm (Melissa officinalis) in Bulgaria from 2003 to 2013 based on mathematical approaches. Correlation and regression analyses have been applied using the capabilities of the IBM Statistics SPSS 24 and the MS Excel 2010 software. The study proves the existence of positive correlations between ‘year’ and ‘yield’ of the lemon balm (r=0.609*), between oil-yielding rose and lavender (r=0.620*) and between lavender and coriander (r=0.766**) and negative association between ‘year’ and the peppermint yield (r=-0.700*). Between yields of other crops – oil-yielding rose, coriander and lavender, and between year and the yields from these crops there are no statistically proven relations. Linear regression equations are presented, showing the relation between the year and the quantity of lemon balm and peppermint production.