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three categories of patients (those entering in fair, serious and critical condi

ID: 3132178 • Letter: T

Question

three categories of patients (those entering in fair, serious and critical condition) and the survival rate from surgery (in percent) for the two local hospitals.

Patient Entering Condition

Hospital A

Hospital B

Survivors from A (# and percent)

Survivors from B (# and percent)

Fair

700

100

600 or 86%

90 or 90%

Serious

200

200

100 or 50%

150 or 75%

Critical

100

700

10 or 10%

300 or 43%

Total

1000

1000

710 or 71%

540 or 54%

Looking at the data broken down in this way, we see that Hospital B has a higher success rate in all three categories of patients but when averaged all together, Hospital A has the higher overall survival rate. Based on the numbers presented, which hospital do you think is superior in cardiac surgery?

three categories of patients (those entering in fair, serious and critical condition) and the survival rate from surgery (in percent) for the two local hospitals.

Patient Entering Condition

Hospital A

Hospital B

Survivors from A (# and percent)

Survivors from B (# and percent)

Fair

700

100

600 or 86%

90 or 90%

Serious

200

200

100 or 50%

150 or 75%

Critical

100

700

10 or 10%

300 or 43%

Total

1000

1000

710 or 71%

540 or 54%

Explanation / Answer

Here the simple mean of survival rate takes number of patients entering the hospital as weight.

Since the survival rate for fair condition patient is higher and for hospital A number of such patients is 700 (highest), it pulls the mean to a higher value.

Since the survival rate for critical condition patient is lower and for hospital B number of such patients is 700 (highest), it pulls the mean to a lower value.

Hence comparison of overall mean would not give any idea about which hospital is better.

It is better to compare the individual percentages. From those values it can be concluded that hospital B is superior in cardiac surgery. One may also argue that the survival rate for critical condition patient in A is 10% whereas the same for B is 43%. From this point of view, B is the superior hospital.