Suppose we want to compute a two-sided 95% CI for the true mean change in the fruits-and-vegetables group minus the true mean change in the control group, which we represent by (c₁, c₂). Without doing any further calculations, which of the following statement(s) must be false?

(1) The lower confidence limit (c₁) = −5.0.

(2) The upper confidence limit (c₂) = −1.0.

(3) The width of the CI (c₂ − c₁) = 3.0.

[Note: The actual values of c₁, c₂, or (c₂ − c₁) may differ from given above.] 

Hypertension

A study was recently reported comparing the effects of different dietary patterns on blood pressure within an 8-week follow-up period [16]. Subjects were randomized to three groups: A, a control diet group, N = 154; B, a fruits-andvegetables diet group, N = 154; C, a combination-diet group consisting of a diet rich in fruits, vegetables, and lowfat dairy products and with reduced saturated and total fat, N = 151. The results reported for systolic blood pressure (SBP) are shown in Table 8.29.

Table 8.29: Effects of dietary pattern on change in SBP

Mean change in fruits-and-vegetables group …………………………. −2.8 mm Hg

Minus mean change in control group (97.5% CI) …………………… (−4.7 to −0.9)