The Two Paragraphs Below Discuss Aspects of Two Studies, Each

question 24

Essay

The two paragraphs below discuss aspects of two studies, each of which exhibit a bias. For each study, decide whether the problem is selection bias, response bias, or nonresponse bias, and in a few sentences explain why you chose your answer. (a) One part of the Nurses' Health Study is concerned with possible causes of skin cancer. Nurses were asked about different behaviors and aspects of their health when they entered the study. Then, the nurses were given the questionnaire again if they were diagnosed with cancer. When the questionnaires were analyzed, the investigators discovered that after the nurses were diagnosed with cancer they tended to report a reduced ability to tan. It is thought that the shift in reporting might be caused by an awareness of their diagnosis. (b) One part of the Demographic and Health Surveys Program is concerned with measures of malnutrition. Investigators measure physical aspects of growing children, and attempt to document the physical characteristics of a population at different ages. Sadly, in some countries many children die early, and thus a bias is introduced in the study when the investigators can not collect the data from the deceased children.

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Definitions:

Water Infiltration

The process by which water on the ground surface enters the soil, replenishing groundwater and soil moisture.

Percolation

The process by which a liquid slowly passes through a filter or porous substance.

Aeration

The process of introducing air into a material, such as soil or water, to improve oxygenation and reduce compaction or concentration of gases.

Nutrient-holding Capacity

The ability of soil to retain nutrients and make them available to plants, influencing soil fertility and agricultural productivity.