A psychologist wanted to study the effect of illicit drug use on one’s ability to focus or concentrate. The psychologist measured 40 participants’ ability to focus before and after taking a controlled amount of an illicit drug.  In the results section, the psychologist writes: "There was a significant decline in focus/concentration from a mean of 18.41 (SD = 2.48) to 11.44 (SD = 2.69), t (39) = 10.87, p < .01 (one-tailed)."

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
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Chapter10: Statistics
Section10.6: Summarizing Categorical Data
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  • A psychologist wanted to study the effect of illicit drug use on one’s ability to focus or concentrate. The psychologist measured 40 participants’ ability to focus before and after taking a controlled amount of an illicit drug.  In the results section, the psychologist writes: "There was a significant decline in focus/concentration from a mean of 18.41 (SD = 2.48) to 11.44 (SD = 2.69), t (39) = 10.87, p < .01 (one-tailed)."

a. What kind of t-test was used by the psychologist?  Why?

b. Elaborate on each facet of the t-test results as you explain the impact of illicit drugs in this experiment.

 

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