TABLE 12-9
Four Surgical Procedures Currently Are Used

question 63

True/False

TABLE 12-9
Four surgical procedures currently are used to install pacemakers. If the patient does not need to return for follow-up surgery the operation is called a "clear" operation. A heart center wants to compare the proportion of clear operations for the 4 procedures, and collects the following numbers of patients from their own records:
$$\begin{array}{l}\text {\quad\quad\quad\quad\quad\quad\quad Procedure }\\\begin{array} { l | r r r r | r } & \text { A } & \text { B } & \text { C } & \text { D } & \text { Total } \\\hline \text { Clear } & 27 & 41 & 21 & 7 & 96 \\\text { Return } & 11 & 15 & 9 & 11 & 46 \\\hline \text { Total } & 38 & 56 & 30 & 18 & 142\end{array}\end{array}$$ They will use this information to test for a difference among the proportion of clear operations using a chi-square test with a level of significance of 0.05.
-Referring to Table 12-9, there is sufficient evidence to conclude that the proportions between procedure B and procedure D are different at a 0.05 level of significance.

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Definitions:

Independent Variable

The variable that is manipulated in an experiment to see its effect on a dependent variable.

Interactions

In research, refers to the way that different factors or variables influence each other, often changing the outcome or effects when combined.

Internal Validity

The extent to which a study can prove that a cause-and-effect relationship exists between the tested variables, excluding the influence of external factors.

Nonmonotonic Relationship

A relationship between two variables where the direction of the effect changes over the range of the variable, meaning it can increase then decrease, or vice-versa.