Cortisol is a hormone that plays an important role in mediating stress. There is
ID: 3226481 • Letter: C
Question
Cortisol is a hormone that plays an important role in mediating stress. There is growing awareness that expo-sure of outdoor workers to pollutants may impact cortisol levels. The article "Plasma Cortisol Concentration and Lifestyle in a Population of outdoor Workers" (Intl. J. of Envir. Health Res., 2011: 62-71) reported on a study involving three groups of police officers: (1) traffic police (TP), (2) drivers (D), and (3) other duties (0). Here is summary data on cortisol concentration (ng/ml) for a subset of the officers who neither drank nor smoked. Assuming that the standard assumptions for one-way ANOVA are satisfied, carry out a test at significance level .05 to decide whether true average cortisol concentration is different for the three groups.Explanation / Answer
Hypotheses are:
Ho: The true average cortisol concentration is same for three groups.
Ha: The true average cortisol concentration is not same for three groups.
Following is the output of ANOVA analysis:
Since p-value is greater than 0.05 so we fail to reject the null hypothesis. That is we cannot conclude that the true average cortisol concentration is different for three groups.
ANOVA SS df MS F p-value Between 11223.5263 2 5611.7632 2.6935 0.0714 Within 270845.35 130 2083.4258 Total 282068.8763 132