In the article “Relationship of collegiate football experience and concussion with hippocampal volume and cognitive outcomes” published in JAMA (Singh, et al., 2014), the authors reported the results of a study assessing the relationship between concussion history and years of football experience with hippocampal volume in collegiate football athletes. Use summary statistics given in Table 7.42 to answer the following questions.

(a) Based on the information in Table 7.42, is it reasonable to assume that ???????? = ?????????
Why?

(b) Compute the appropriate value of ????????(????̄ − ????̄) and determine its degrees of freedom.

(c) Determine the rejection region for testing ????0 ∶ ???????? ≤ ???????? when ???? = 0.05.

(d) Compute the value of ????obs and its approximate ????-value.

(e) Is there sufficient statistical evidence to conclude ???????? > ????????? Why?

(f) Compute a 95% confidence interval for ???????? − ????????.

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Number of Average StDev 95% CI Resamples Difference of Difference for Difference 1000 -2.4667 1.140 (-4.6716, -0.1446)