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t-Test for Two
CHAPTER 10

Independent/

Unrelated Samples

s any college student would tell you, high school was easy com-
Learning Apared to the requirements, classes, and assignments in college. It’s
Outcomes not like you weren’t warned. When your high school teachers weren’t

After reading this chapter, you focused on telling you to put your phone away, they were trying to
should be able to: scare you into getting prepared for college. Because college influences
• Explain the key question that a your career success, the appeal of being better, faster, stronger, and
t-test for two independent samples
seeks to answer. smarter is real. And even though you’re in college, it’s never too late
• Identify similarities and to start flexing those cognitive muscles. After all, we exercise to make

differences between a t-test for two our body stronger. Perhaps we need to do the same for our brain as
independent samples and other well. Work smarter, not harder.
t-tests. As it turns out, there’s an app for that. There are many brain-training
• Describe the underlying logic for apps available now that promise to enhance mental abilities, sharpen
calculating a pooled estimate of the cognition, and boost IQ by doing fun games. Allegedly.
population variance.
• Identify when it is appropriate The question is, do they really work? Well, there are several signs

to use a t-test for two independent that the brain-training app’s claims are legitimate. For example, when
samples. you go to brain-training sites, they give a lot of supporting information
• Find a cutoff score in a t-table. about their millions of users, a board of credentialed scientists, research
• Describe the underlying logic partners, and pervasive use of the word “science.” But is it really sci-
for combining the variances from ence? Part of being psychologically literate and a good consumer of
both distribution of means when scientific information is knowing what type of evidence is necessary
calculating a variance for the to be truly convinced. You need to test it out.
distribution of differences between
means.
• Calculate the t-score for the Statistics for Life
t-test for two independent samples. First, you’ve been a behavioral science student long enough
• Describe the assumptions of the to know that checking the existing literature is always a
t-test for two independent samples.
good idea. When you do, there’s an article, “Do ‘Brain-
Training’ Programs Work?” that reviews brain-training research
(Simons et al., 2016), and another, “Toward a Science of Effective
Cognitive Training” (Smid et al., 2020), both of which cast serious
doubt on programs’ claims. However, one study with a large sample
of 4,715 people found that brain-training, when compared to com-
pleting crossword puzzles, had a range of benefits such as quicker

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