TABLE 13-12
the Manager of the Purchasing Department of a Large

TABLE 13-12
The manager of the purchasing department of a large banking organization would like to develop a model to predict the amount of time (measured in hours) it takes to process invoices. Data are collected from a sample of 30 days, and the number of invoices processed and completion time in hours is recorded. Below is the regression output:
$$\begin{array} { l c } { \text { Regression } \text { Statistics } } \\\hline \text { Multiple R } & 0.9947 \\\text { R Square } & 0.8924 \\\text { Adjusted R Square } & 0.8886 \\\text { Standard Error } & 0.3342 \\\text { Observations } & 30 \\\hline\end{array}$$ $\text{ANOVA}$

$\begin{array}{llcc}&\text { df} &\text {SS } &\text {M S}&\text { F}&\text { Significance F}\\\text { Regression } &1&25.9438&25 .9438&232 .2200&4 .3946 \mathrm{E}-15\\\text {Residual }&28 &3.12820 .1117 \\\text { Total } & 29 & 29.072\end{array}$


-Referring to Table 13-12, the degrees of freedom for the t test on whether the number of invoices processed affects the amount of time are

A) 1.
B) 28.
C) 30.
D) 29.