Question

(b) a tooth - whitening gel is to be tested for effectiveness. a group of 85 adults have volunteered to participate in the study. of these, 43 are to be given a gel that contains the tooth - whitening chemicals. the remaining 42 are to be given a similar - looking package of gel that does not contain the tooth - whitening chemicals. a standard method will be used to evaluate the whiteness of teeth for all participants. then the results for the two groups will be compared. (select all that apply.) after the treatment period, compare the whiteness of the 43 treated adults. the remaining 42 adults receive the placebo gel. after the treatment period, compare the whiteness of the two groups. randomly select 85 adults to be given the treatment gel. randomly select 43 adults to be given the treatment gel. a placebo is not being used. how could this experiment be designed to be double - blind? the patients would not know which gel they or the other patients are receiving. the treatment administrators would not know which gel the patients are receiving. neither the treatment administrators nor the patients would know which gel the patients are receiving. the patients would not know which gel they are receiving.

Explanation:

In the experiment, 43 get treatment gel, 42 get placebo. Double - blind means neither patients nor administrators know.

Answer:

For first part: The remaining 42 adults receive the placebo gel., After the treatment period, compare the whiteness of the two groups., Randomly select 43 adults to be given the treatment gel.
For second part: Neither the treatment administrators nor the patients would know which gel the patients are receiving.