Question

Valve surgery Medical researchers want to compare the success rate of a new non invasive method for replacing heart valves using a cardiac catheter with traditional open heart surgery. They have $40$male patients, ranging in age from $55$to $75$, who need valve replacement. One of several response variables will be the percentage of blood that flows backward in the wrong direction-through the valve on each heartbeat.

a. Design an experiment that uses a completely randomized design to investigate this question.

b. Design an experiment that uses a matched pairs design to investigate this question. Explain your method of pairing.

c. Which design do you prefer? Explain your answer.

Short answer

(a) The experiment that uses a completely randomized design to investigate is assigning unique no. between one and forty.

(b) The experiment that uses a matched pairs design to investigate is dividing group of forty patients into groups of two patients each.

(c) The preferred design is matched pair experiment.

Step-by-step solution

Part (a) Step 1: Given information

We need to find the experiment that uses a completely randomized design to investigate.

Part (a) Step 2: Explanation

All subjects are randomly assigned to a group in a truly randomized experiment.

Let's give each of the forty patients a unique number between one and forty (inclusive).

Using slips of paper, a random digits table, or technology, randomly generate twenty distinct numbers between one and forty (inclusive).

The novel non-invasive approach will be assigned to the twenty patients corresponding to the twenty selected integers, while the traditional open-heart surgery will be assigned to the remaining twenty patients.

Part (b) Step 1: Given information

We need to find an experiment that uses a matched pairs design to investigate.

Part (b) Step 2: Explanation

A matched pairs experiment contrasts two treatments that each participant receives, or two subjects who are highly similar.

Let's divide the forty male patients into two groups of two, with the two patients in each group being as similar as feasible (age, health, etc.).

One person in each group is randomly assigned to the novel non-invasive approach, while the remaining people are randomly assigned to standard open-heart surgery.

The percentage of blood that flows backwards for the two treatments is then compared.

Part (c) Step 1: Given information

We need to find the preferred design.

Part (c) Step 2: Explantion

We prefer the matched pairs experiment because there are more subjects assigned to each treatment than in a completely randomized experiment, and the two treatment groups are identical before the treatments begin, making it easier to compare treatment results and the differences in results more reliable (that is, we are more certain that the differences are due to the treatments).