Plasma homocysteine levels are measured in patients with acute coronary syndrome who are treated at a large community hospital. The mean plasma homocysteine level in this group is determined to be 11.1 µmol/L with a standard deviation of 1.2 µmol/L. In a separate group of patients hospitalized on the general ward in the same hospital, the mean plasma level is 9.5 µmol/L and the standard deviation is 1.3 µmol/L. Which of the following statistical methods should be used to compare the mean homocysteine levels of these 2 groups of patients?

Question

Plasma homocysteine levels are measured in patients with acute coronary syndrome who are treated at a large community hospital.  The mean plasma homocysteine level in this group is determined to be 11.1 µmol/L with a standard deviation of 1.2 µmol/L.  In a separate group of patients hospitalized on the general ward in the same hospital, the mean plasma level is 9.5 µmol/L and the standard deviation is 1.3 µmol/L.  Which of the following statistical methods should be used to compare the mean homocysteine levels of these 2 groups of patients?

Quizplus · Accepted Answer

11ec160b_3728_935c_9249_f5add6af3c4e_MD0001_00 The two-sample t test is commonly employed to determine if the means of 2 populations are equal. Several statistical approaches can be used, but the basic numerical requirements needed to perform this test are the 2 mean values, the sample variances (eg, standard deviations), and the sample sizes. The t statistic is then calculated, from which the p value can be determined. If p < 0.05, the null hypothesis (which assumes that there is no difference between 2 groups) is rejected and the 2 means are assumed to be statistically different. (Choice B) Linear regression is used to model the linear relationship between a dependent variable and an independent variable. For example, linear regression could be used to determine the relationship (described in terms of a trend line) between the number of cigarettes smoked per day and the number of yearly hospitalizations in COPD patients. (Choice C) The correlation coefficient is a measure of the strength and direction of a linear relationship between 2 variables. For example, a study may report a correlation coefficient describing the association between estrogen levels and breast cancer risk in postmenopausal women. It is different from linear regression in that a single number is reported describing the strength and magnitude of the association. (Choice D) The chi-square test is most appropriate for use with categorical data. It can be used to evaluate whether the expected frequency of an occurrence is consistent with the observed frequency of that occurrence ("goodness of fit"). For instance, a study evaluating Mendelian inheritance of red and green seed colors would use a chi-square test to compare the observed and expected proportions of each seed type. (Choice E) Meta-analysis is an epidemiologic method of analyzing pooled data from several studies, thereby increasing the statistical power beyond that of the individual studies. Educational objective: The two-sample t test is a statistical method commonly employed to compare the means of 2 groups of subjects.

Plasma Homocysteine Levels Are Measured in Patients with Acute Coronary