A Screening Test for a Certain Disease Is Used in a Large

question 9

Essay

A screening test for a certain disease is used in a large population of people of whom 1 in 1000 actually have the disease. Suppose that the false positive rate is 1% and the false negative rate is 0.5%. Thus a person who has the disease tests positive for it 99.5% of the time, and a person who does not have the disease tests negative for it 99% of the time.
(a) What is the probability that a randomly chosen person who tests positive for the disease actually has the disease?
(b) What is the probability that a randomly chosen person who tests negative for the disease actually has the disease?

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Definitions:

Light-Dependent Reactions

The first stage of photosynthesis where light energy is converted into chemical energy in the form of ATP and NADPH.

Light-Independent Reactions

A series of biochemical reactions in photosynthesis that do not require light to proceed, resulting in the synthesis of glucose from carbon dioxide and water.

Photosynthesis

The process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose, releasing oxygen as a byproduct.

Chloroplast

An organelle found in plant and algae cells where photosynthesis takes place, converting light energy into chemical energy stored in glucose.