The paper \"Effect of Long-Term Blood Pressure Control on Salt Sensitivity\"[jou

Question

The paper "Effect of Long-Term Blood Pressure Control on Salt Sensitivity"[journal of medicine (1997) 28:147-156] describes a study evaluating salt sensitivity (SENS) after a period of antihypertensive treatment. Ten hypertensive patients (diastolic blood pressure between 90 and 115mmHg) were studied after at least 18 months on antihypertensive treatment. SENS readings, which were obtained before and after the patients were placed on an antihypertensive treatment, are given here. Is there significant evidence that the mean SENS value decreased after the patient received antihypertensive treatment? Estimate the size of the change in the mean SENS value. Do the conditions required for using the t procedures appear to be valid for these data? Justify your answer.

Explanation / Answer

Solution

Let D = SENS value before treatment - SENS value after treatment. i.e., d represents the change in SENS value. D follows a Normal Distribution with mean µ and variance 2.

To test significant difference,

Null Hypothesis H0: µ = 0, i.e., there is no significant reduction and HA: µ > 0.

Test Statistic: t = (n)(D bar - µ)/s, where D bar = average of D from the sample, s = sample standard deviation and n = sample size.

Under H0, t has a t-distribution with (n - 1) degrees of freedom.

Decision criterion: Reject H0, if tcal (i.e., calculated value of t) > upper % point of t-distribution with (n - 1) degrees of freedom, where = level of significance.

From the given data, D bar = 2.584; s = 9.491; n = 10 and hence tcal= 0.861

Since question does not specify , the most frequently value of 5% is taken to be .

From Standard t-distribution table,

upper 5% point of t-distribution with 9 degrees of freedom = 1.833.

Since tcal < 1.833, H0 is accepted implying that there is no significant evidence that mean SENS value has decreased after treatment.

b) The size of decrease in SENS value = 2.584

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.