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).
In order for implantation to take place, ovulation and fertilization must occur first. Implantation happens early in the pregnancy stage after the fertilized egg (zygote) travels down the fallopian tube to the uterus and adheres to the epithelium, or uterine lining. It takes about eight to 10 days for the fertilized egg to travel to the uterus.