Which of the following is an extremely important design element to have in an experimental study? check all that apply. a.treatments that are imposed by the experimenterb. a placeboc. groups which are exactly the same sized. randomized selection of participants

a.Treatments that are imposed by the experimenter

b.A placebo

d.Randomized selection of participants

Step-by-step explanation:

In order to design an experiental study w eneed to take in count 5 important things and are described below:

1) Control

We always need to have a control group in order to compare the results of the experiment, that's extremely important in order to don't introduce bias to the experiment.

2) Randomization

That condition is useful in order to eliminate bias using only their expert judgment, the use of randomization in experimment. "In a randomized experimental design, objects or individuals are randomly assigned (by chance) to an experimental group. Using randomization is the most reliable method of creating homogeneous treatment groups, without involving any potential biases or judgments".

We can use for example different methods like: Randomized Block Design or Completely Randomized Design

Completely Randomized Design : "objects or subjects are assigned to groups completely at random"

Randomized Block Design: "subjects are first divided into homogeneous blocks before they are randomly assigned to a treatment group"

3) Treatments

From the definition means " something that researchers administer to experimental units". And needs to be defined the treatments in order to design any experimental study.

4) Factor

A factor of an experiment "is a controlled independent variable; a variable whose levels are set by the experimenter".

5) Replication

That condition means "the repetition of an experiment on a large group of subjects, is required". And it;s important to ensure this.

Based on this the correct options would be:

a.Treatments that are imposed by the experimenter

b.A placebo

d.Randomized selection of participants

$25

step-by-step explanation:

25 - 4.50 = 20.5

20.5 / 2 = 10.25

10.25 + 10 = 20.25

20.25 - 12.50 = 7.75

therefore the answer is $25 as shown as the first number.

step-by-step explanation:

6.48/4 4 goes into 6.48 1.62 times