DRAINAGE RESEARCH IN FARMERS’ FIELDS: ANALYSIS OF DATA Part of project “Liquid Gold” of the International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands. R.J.Oosterbaan, July 2002
On website https://www.waterlog.info public domain, latest upload 20 11 2017
TABLE OF CONTENTS
1. Analysis of data...... 2 1.1 Types of analysis ...... 2 1.2 Parameters ...... 2
2. Standard statistical analysis...... 4 2.1 Frequency analysis ...... 4 2.2 Time series analysis ...... 21 2.3 Testing of differences ...... 27 2.4 Spatial differences ...... 29 2.5 Correlation analysis ...... 30
3. Conceptual statistical analysis...... 33 3.1 Linear regression, ratio method ...... 34 3.2 Linear regression, least squares method ...... 35 3.3 Intermediate regression ...... 44 3.4 Segmented two variable linear regression ...... 48 3.5 Segmented three variable linear regression ...... 56 3.6 Partial segmented linear regression ...... 60
4. Conceptual deterministic analysis...... 61 4.1 Introduction ...... 61 4.2 Transient recharge discharge relations ...... 63
References...... 70
Note : for additional information on section 3.4 see article on website: https://ww.waterlog.info/pdf/segmregr.pdf 2
1. Analysis of data
1.1 Types of analysis
In drainage pilot areas one collects a large number of data that usually show a large variation (scatter). The analysis of the data aims at reaching conclusions, despite the scatter, on the drainage aspects of the pilot area proper, and recommendations for application to a wider area. The methods of analysis can be distinguished three types: