☹ Oops. Cell 2 represents a serious error. Here, we have rejected the null hypothesis (that there is no difference) when it is really true (and there is no difference between groups). Even though there is no difference between the two groups of children, we will conclude there is, and that’s an error—clearly a boo-boo, called a Type I error. ☹ Uh-oh, another type of error. Cell 3 represents a serious error as well. Here, we have accepted the null hypothesis (that there is no difference) when it is really false (and, indeed, there is a difference between groups). We have said that even though
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