In order to investigate treatments for morbid obesity, obese subjects satisfying fairly strict requirements were randomly assigned to one of three groups: gastric bypass surgery; participation in a diet and exercise program; or both gastric bypass surgery and participation in the diet and exercise program. researchers carefully observed the amount of weight lost five years after the study began. this study uses the principles of a. randomization. b. confounding. c. blocking. d. all of the above

A randomization

Step-by-step explanation:Randomization in scientific experiments is a sampling method in which the participants or researchers are chosen randomly and assigned a treatment.

Here the participants or researchers do not know for sure which treatment is better.

Randomization reduces any possible bias responses to a minimal.

  q

step-by-step explanation:

each line from a vertex to the midpoint of the opposite side is called a median. the point where the medians intersect, point q, is the centroid.

the centroid of δabc is point q.

1350 hats

step-by-step explanation:

divide 900 by 2 to find 50% or half of 900

900/2=450

add 450 to 900

1350