Researchers randomly choose two groups from 15 volunteers. over a period of 9 weeks, one group watches television before going to sleep, and the other does not. volunteers wear monitoring devices while sleeping, and researchers record dream activity. which type of study method is described in each situation?
a. not enough information given.
b. observational study
c. survey
d. controlled experiment

Option D. Controlled experiment

Step-by-step explanation:

A. The information given is sufficient to identify the type of study method in each situation.

B. In observational study, the researcher has no control over the variables and no treatment is applied on the variables. But in case 1, only one group is allowed to watch television (controlled) and in case 2 volunteers wear monitoring devices while sleeping ( treatment is applied ) so not observational study

C. Survey study includes collecting the information or data as reported by the individuals but in the given situations the volunteers are not reporting any information to the researchers instead they are monitored and controlled by the researchers. So, not survey study

D. A controlled experiment is one in which the variables are manipulated by the researchers and here in all the cases the researchers are controlling the volunteers in one way or other so in both the situations controlled experiment study is described

Hence, the option D is appropriate.

d

step-by-step explanation:

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.