BASIC CONCEPTS OF PHYTOPATHOLOGICAL RESEARCH TERMS

VARIABLE:

Characteristics which show variation from one individual to another individual or from one material to another material or one treatment to another treatment known as variable. E.g. plant height, length, fruit color, taste, fruit size, disease incident etc.

TYPES OF VARIABLES:

Variables can be expressed in two ways.

1.     Quantitative variable.

2.     Qualitative variable.

1.     Quantitative Variable:

The characteristics which can be expressed or measured numerically are known as quantitative variable. E.g. size of spore, conidia, disease severity, disease incident etc.

         

2.     Qualitative Variable:

The characteristics which cannot be expressed or measured numerically are known as qualitative variable. E.g. color, taste, flavor, merit etc.

TREATMENT:

The different materials / methods / conditions whose effects are to be tested / measured in the experiment are known as treatment. E. g. doses of fungicide, temperature requirement for sporulization, method of inoculation etc.

EXPERIMENTAL UNIT:

Experimental unit is the theme to which the treatment to apply to measure the variable to the study. E. g. unit plot, individual plant, individual fruit etc.

POPULATION:

Totality of individual / collection of individual is called the population. E. g. mass of spore, bacteria, fungi etc, human wheat plant etc. living experiment will not be possible without population.

SAMPLE AND SAMPLING:

Sample:

The representative of a population is known as sample.

Sampling:

It means representation of a sample. E. g. while taking mean weight and height of 5 persons to represent 20 persons, those 5 persons are sample and the process is sampling.

DATA:

Information about the observation is called data.

EXPERIMENTAL ERROR:

It is the measure of variation which exists among the observations on the experimental unit treated alike.

A part of the variation is systematic and cannot be explained where remaining variation is random. The unexplained random part of the variation is termed as experimental error.

Experimental error includes all type of extra sources of variation due to-

1.     Inherent variability of experimental unit

2.     Error associated with the measurement.

3.     Lack of representative of sample.

BIAS:

A measure of the representativeness of the procedure used by the researcher that creates differences between the average result and the true value of the population sample, on a certain variable.

PRECISION:

It means a speech of information on the sensitivity of an experiment and is measured by the reciprocal of the variance of a mean.

Precision =                              1                          

        Error variance

      Replication

  =                         Replication                             

        Error variance

If replication is maximized and error variation is minimized then precision increased.