In the article “Lower-Dose vs High-Dose Oral Estradiol Therapy of Hormone Receptor-Positive, Aromatase Inhibitor-Resistant Advanced Breast Cancer: A Phase 2 Randomized Study” published in JAMA ( Ellis, et al., 2009), the authors reported the results of a two-sample study to evaluate daily doses of 6 mg of estradiol as a viable therapy for postmenopausal women with advanced aromatase inhibitor-resistant hormone receptor–positive breast cancer. Table 7.39 contains the summary statistics for the estradiol levels for treatments of 6 mg and 30 mg of estradiol. Use the information in Table 7.39 to answer the following questions.

(a) Based on the information in Table 7.39, 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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Treatment 6 mg (X) 30 mg (Y) Estradiol Level Sample Size Mean SD 22 29 302 519 23 2403 2268