Researchers wanted to know whether there was a difference in comprehension among students learning a computer program based on the style of the text. They randomly divided 36 students into two groups of 18 each. The researchers verified that the 36 students were similar in terms of educational level, age, and so on. Group 1 individuals learned the software using a visual manual (multimodal instruction), while group 2 individuals learned the software using a textual manual (unimodal instruction). The following data represent scores that the students received on an exam given to them after they studied from the manuals.

(a) What type of experimental design is this?
(b) What are the treatments?
(c) A normal probability plot and boxplot indicate it is reasonable to use Welch€™s t-test. Is there a difference in test scores at the α = 0.05 level of significance?

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51.08 57.03 44.85 75.21 56.87 75.28 57.07 80.30 52.20 Visual Manual 60.35 76.60 70.77 70.15 47.60 46.59 81.23 Textual Manual 64.55 57.60 68.59 50.75 49.63 43.58 57.40 49.48 49.57 56.54 39.91 65.31 51.95 49.07 48.83 72.40 42.01 61.16 67.30 60.82