In double-blind studies neither the test subject or the researcher knows who was given the drug and who was given the control. why are these studies effective for testing a drug that may elevate mood and relieve feelings of depression?
a)since there are two symptoms that are affected, a double-blind study is required.
b)double-blind studies are ways to ensure that only the researcher can figure out who is getting the effective drug.
c)double-blind studies are the most economical way to gather results from testing on humans.
d)the patients and researchers are not given this information so they cannot be influenced in reporting the effectiveness.

The correct answer would be option D.

Double-blind experiment refers to the experimental procedure in which neither the researcher nor the subjects know that which subjects are used as a test group and which subjects are used as control group during the entire course of the experiment.

This experiment is usually used in the experiments in which results can be affected by both conscious as well as unconscious bias on the part of experimenters, subjects, or both.

It reduces all the effects that may arise from preconceived notions or by physical cues such as observer cues, placebo et cetera.

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s