Research design refers to the complete sequence of steps to be undertaken to ensure that the appropriate data will be obtained in a way which permits an objective analysis leading to valid inferences with respect to the stated problem. It is a step in problem solving consisting of a detailed plan to be followed in obtaining the needed data. It specifies what organisms, chemicals, glasswares, and equipment will be used in the study.
1. It serves as a guide for direction during the actual experimentation.
2. It allows a gain of maximum information relevant to the problem at minimum cost.
3. It makes the statistical test of ...view middle of the document...
The number of the replicates needed is based on the degree of precision required, degree of homogeneity of the sample and the number of treatments in the study.
- refers to the assignment of the experimental units to the treatment or vise versa by chance. It assures us a valid or unbiased estimate of population parameters e.g. means and differences between treatments. It assures the validity of the statistical tests of significance.
- refers to the balancing, grouping, and blocking of experimental units that is employed to the adopted design. Blocking is the allocation of the experiment to a block in such a manner that the units within the block are relatively homogeneous. Some bases for blocking are height, age, sex, weight, fertility gradient, and pH gradient.
E. Basic Types of Design
There are basically two types of designs namely: Completely Randomized Design (CRD) and Randomized Complete Block Design (RCBD). The other designs are the variations of these two basic types.
Completely Randomized Design (CRD)
Treatments are randomly assigned to the experimental subjects without restriction. The experimental subjects are assumed to be homogeneous with respect to the factors that could affect the treatments being compared.
Suppose there are 15 experimental subjects, three of which will receive one of five treatments A, B, C, D, or E. The three subjects receiving a particular treatment will be considered three replicates for the treatment. The following steps are called for:
1. Number the experimental subjects from 1 to 15.
2. Select at random a set of 15 three digit numbers from the table of random numbers.
3. Assign ranks to the number: These ranks can be considered random permutation (arrangement) of the numbered 1 to 15 assigned to the experimental subjects.
4. Divide the numbers into 5 groups and assign treatment A to the first group, B of the second group and so on.
Some researchers conduct the randomization in quite a different manner. Using the same sample above, the procedure may be summarized as follows:
1. Number the experimental subjects consecutively from 1 to 15.
2. Select a random number from 1 to 5 representing one of 5 treatments. (This will give each treatment the probability of 1/5 of being selected.)
3. Assign the first experimental subject to the nth treatment if the random number drawn is n (n=1,2….5).
4. Repeat the process until each one of the 15 subjects is assigned to a treatment.
1. the CRD is flexible, in that the number of treatments and replications is limited only by the number of experimental subjects.
2. the statistical analysis is simple and easy, even if the number of replications per treatment is not the same or the experimental error differs from treatment.
3. the statistical analysis remains simple and easy even if some experimental subjects or entire treatments are...