A recent study in the Journal of the American Medical Association (February 20, 2008) found that patients who go into cardiac arrest while in the hospital are more likely to die if it happens after 11 pm. The study investigated 58,593 cardiac arrests during the day or evening. Of those, 11,604 survived to leave the hospital. There were 28,155 cardiac arrests during the shift that began at 11 pm, commonly referred to as the graveyard shift. Of those, 4,139 survived for discharge. The following contingency table summarizes the results of the study:

a. Specify the competing hypotheses to determine whether a patient’s survival depends on the time at which he/she experiences cardiac arrest.

b. At a 1% significance level, find the critical value.

c. Calculate the value of the test statistic.

d. What is the conclusion to the test? Is the timing of when a cardiac arrest occurs independent of whether or not the patient survives for discharge? Given your answer, what type of recommendations might you give tohospitals?

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Survived for Discharge Did Not Survive for Discharge 46,989 24,016 71,005 Row Total 58,593 28,155 86,748 Shift Day or Evening Shift11,60 Graveyard Shift Column Total 4,139 15,743