Astudent researcher conducts an experiment that investigates the effects of a new mathematics website on student achievement. she randomly assigns students to two groups: one that receives supplemental instruction from the website and one that doesn't receive the supplemental instruction. each sample consists of 20 students. observations of student engagement are rated by the researcher, according to an engagement scale. how could this study be improved?

select all that apply.

a.
have another researcher provide ratings, as well.

b.
administer a quiz or exam that gauges student understanding.

c.
increase the sample size.

d.
limit observations to students who are engaged.

A, B and C

Step-by-step explanation:

A. Adding another researcher to provide ratings will make the study less biased.

B. A quiz or exam will show which students have a better understanding of the math material. Better quiz or exam results show that the site is more effective for a student with or without the supplemental instruction.

C. Having a greater sample size is better because a greater scope of students is covered. Different students have different abilities and learning preferences.

A. - Have another researcher provide ratings, as well.

B. - Administer a quiz or exam that gauges student understanding

C. - Increase the sample size.

Step-by-step explanation:

Option A is correct because additional researchers help identify and eliminate bias in individuals.

Option B would be very helpful in obtaining quantitative data on students improvement.

Option C will also improve the study because larger sample sizes mean more accurate results.

Option D is NOT correct, as limiting observations to students who are engaged eliminates the control group and makes it so that there is no baseline, rendering the experiments results almost meaningless.

i need a picture

step-by-step explanation: