How to choose an appropriate experimental design type to arrange research factors and their levels is an important issue in experimental research. Choosing an appropriate design type is directly related to the accuracy and reliability of the research result. When confronting a practical issue, how can researchers choose the most appropriate design type to arrange the experiment based on research objective and specified situation? This article mainly introduces the related contents of the single-group design and the paired design through practical examples.

Three-factor designs that are unable to examine the interactions include crossover design and Latin square design, which can examine three factors, namely, an experimental factor and two block factors. Although the two design types are not quite frequently used in practical research, an unexpected research effect will be achieved if they are correctly adopted on appropriate occasions. Due to the limit of space, this article introduces two forms of crossover design.

Three-factor designs that are unable to examine the interactions include crossover design and Latin square design, which can examine three factors: an experimental factor and two block factors. Although the two design types are not quite frequently used in practical research, an unexpected research effect will be achieved if they are correctly adopted on appropriate occasions. This article introduced the 3×3 crossover design and the Latin square design by examples.

Multifactor designs that are able to examine the interactions include factorial design, factorial design with a block factor, repeated measurement design; orthogonal design, split-block design, etc. Among all the above design types that are able to examine the interactions, the factorial design is the most commonly used. It is also called the full-factor experimental design, which means that the levels of all the experimental factors involved in the research are completely combined, and k independent repeated experiments are conducted under each experimental condition. The factorial design with a block factor can also examine the influence of a block factor formed by one or more important non experimental factors based on the factorial design. This article introduces the factorial design and the factorial design with a block factor by examples.

The general problems existing in the clinical trials of investigational new drugs involve some key aspects such as the guiding principles, research designs, quality controls and statistical analyses. This paper explores the eight general issues in the clinical trials of investigational new drugs and presents precautionary measures with high operability. Research on the clinical trials of investigational new drugs is a complex project, which should be carried out strictly according to the policies, laws, criteria and operating rules set by related agencies. The neglect of research designs and data analyses will lead clinical trials to failure.

The etiology of Crohn's disease is not clear as yet,many evidences has shown that the dysfunction of the immune system is the internal cause of inflammation and tissue damage.It is identified that many immune diseases can be anticipated,monitored and therapeutic through detecting some specified serological markers.To identify some high specific sensitive and predictable markers and groups,the research of searching an ideal and non-incursive method for differentiating inflammatory bowel diseases from other disease is still undergoing.The current research of five serum immune markers that are usefulness in the diagnosis and management of Crohn's disease are summarized.

Thymosin ?1 is a multiple peptide of hormone and protein isolated from thymus gland,and it has many biological functions.It has been reported that it plays an important role in immune response,neuroendocrine modulation and gene expression.The article is to review the progress of thymosin ?1 and its mechanisms.