Pretesting is a broad term that incorporates many different methods or combinations of methods. This pamphlet briefly describes eight suggested techniques that can be used to pretest questionnaires. These techniques have different strengths and weaknesses. They can be invaluable for identifying problems with draft questionnaires and also for evaluating surveys in the field.
Illustration depicting ovulation and fertilization. Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the uterine tube. The result of this union is the production of a zygote cell, or fertilized egg, initiating prenatal development.Scientists discovered the dynamics of human fertilization in the nineteenth century.y convention, gestational age is calculated by adding 14 days to fertilization age and vice versa. In fact, however, fertilization usually occurs within a day of ovulation, which, in turn, occurs on average 14.6 days after the beginning of the preceding menstruation (LMP).
Fertilization occurs when the nucleus of both a sperm and an egg fuse to form a diploid cell, known as zygote. The successful fusion of gametes forms a new organism.he nucleus of the oocyte is called a pronucleus in this process, to distinguish it from the nuclei that are the result of fertilization. The sperm's tail and mitochondria degenerate with the formation of the male pronucleus.