How can scientific studies control for the Hawthorne effect, ...

[frankwu]

How can scientific studies control for the Hawthorne effect, placebo effect, and researcher bias?

Question 2

Synthesis of norepinephrine and collagen requires _____.
 a. selenium
  b. zinc
  c. copper
  d. iron

[ebe]

Answer to Question 1

To control for Hawthorne effect, placebo effect, and researcher bias, scientists use blinding (especially double-blinding); use randomization; and control for confounding variables.

Answer to Question 2

c

[frankwu]

Thanks for the timely response, appreciate it

[juliaf]

Gracias!