Advantages and disadvantages of absolute measure of dispersion
Answers
Merits
They indicate the dispersal character of a statistical series.
They speak of the reliability, or dependability of the average value of a series.
They enable the statisticians for making a comparison between two or more statistical series with regard to the character of their stability or consistency.
They facilitate in controlling the variability of a phenomenon under his purview.
They facilitate in making further statistical analysis of the series through the devices like co-efficient of skewness, co-efficient of correlation, variance analysis etc.
They supplement the measures of central tendency in finding out more and more information relating to the nature of a series.
Demerits
They are liable to misinterpretations, and wrong generalizations by a statistician of based character.
They are liable to yield inappropriate results as there are different methods of calculating the dispersions.
Exception on or two, of the methods of dispersion involve complicated process of computation.
They may give a value of variation, which may not be practically found with the items of the series.
They, by themselves, cannot give any idea about the symmetricity, or skewed character of a series.
Like the measures of central tendency, most of the measures of dispersion do not give a convincing idea about a series to a layman.
Answer:
Merits and Demerits of Bulk Breeding Method:
Merits:
1. Bulk breeding is a simple, convenient and less expensive method of crop improvement.
2. In this method natural selection operates which results in elimination of undesirable genotypes from the bulk population and increases the frequency of desirable plants.
3. The chances of obtaining transgressive segregants are more in this method than pedigree method, because the material is grown in large plots in this method.
4. This method is useful to study the competitive ability of various genotypes in the population.
5. This method leads to improvement in adaptation of genotypes due to bulk period. Thus varieties developed by this method are more adaptable than those evolved by pedigree method.
6. There is no need to maintain pedigree records in this method.
This method has been used only in few crops due to time lag. It has been used in the improvement of barely in USA and more than 50 varieties have been developed from composite crosses by this method. In India, only one variety “Narendra Rai” has been developed in Brown Mustard by this method. Thus bulk method has limited application in practical plant breeding.
Demerits:
1. This method does not provide information about the mode of inheritance of various oligogenic characters which is obtained in pedigree method.
2. The long-term bulking requires 20-30 generations and short-term bulking requires 6-10 generations. Thus this method takes more time than pedigree method in release of new variety. For this reason this method is not preferred by the plant breeders.
3. It is difficult to assess the variability in the population and genotypic frequencies in this method, because they change in each generation of bulking.
4. Sometimes, natural selection may favour undesirable than desir