Epidemiology discussion

Epidemiology discussion
Please write a 200-300 word response to the following discussion question.  expect your response to reflect critical thought based on information from the textbook and from one additional source. Whenever possible, try to relate the discussion question to your own experiences. Be sure to appropriately cite and list your references.
Required Textbooks:
Gordis, L. (2014). Epidemiology (5th ed.). Philadelphia, PA: Elsevier. ISBN: 978-1-4557-3733-8 Heymann, D.L. (Ed.) (2015). Control of Communicable Diseases Manual (20th ed.). Washington D.C.: American Public Health Association. ISBN: 978-0-8755-3018-5
Discussion Question: What is the relationship between validity and reliability? Describe a screening or diagnostic test that could be used for an epidemiological investigation and explain the importance of reliability and validity in relation to that test.