Researchers want to investigate if students retain more information if it printed on blue paper rather than white paper. They recruit 100 elementary students, 100 middle school students, and 100 high school students to participate. The researchers then randomly assigned half of the elementary students, half of the middle school students, and half of the high school students to receive the information on blue paper. The remaining students receive the same information on white paper. Required:
Write down the best describes this experimental design.

Stratified design with color of paper as the blocks.

The experimental design that this question uses is the stratified design with color of paper as the blocks

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Stratified design with color of paper as the blocks

Step-by-step explanation:

The experimental design that this question uses is the stratified design with color of paper as the blocks

A stratified design is one where the population has been divided into strata that are homogeneous. A good number of participants would then be picked for each of the stratum. The homogeneous strata are also known as the blocks and here in this question we have color of paper as the block here.

The students are of different school levels, elementary, high school and middle school. Each of these levels have 100 students. The students in each levels are halved and each half is randomly assigned information on either a white paper or a blue paper.

x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81