Researchers fed a small 1.6-ounce bar of dark chocolate to each of 16 randomly s

Question

Researchers fed a small 1.6-ounce bar of dark chocolate to each of 16 randomly selected subjects daily for two weeks. Half of the subjects were randomly selected and assigned to receive bars containing dark chocolate’s typically high levels of flavonoids, and the other half received placebo bars with just trace amounts of flavonoids. Improvement in blood flow were measured in nmol/L. Due to the small sample sizes involved, the researchers choose to use a non-parametric test. The R output below gives the data and the results:

> treatment_group <- c(138, 147, 144, 157, 158, 147, 156, 151)

> control_group <- c(123, 123, 126, 134, 145, 119, 127, 116)

> wilcox.test( treatment_group , control_group )

-----------Wilcoxon rank sum test with continuity correction

data: treatment_group and control_group
W = 62, p-value = 0.001918
alternative hypothesis: true location shift is not equal to 0

State the null and alternative hypotheses, state the test statistic value, state the p-value, and based on the output state your conclusion in the context of the problem.

Explanation / Answer

H0: Means are same Vs H1: Means are not same

Wilcoxon signed rank test

data: treatment_group and control_group
V = 36, p-value = 0.007813
alternative hypothesis: true location shift is not equal to 0

at 0.05 level of significance

P-value is less than 0.05

Accept Null hypothesis

Means are same

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