TABLE 18-5
a Manufacturer of Computer Disks Took Samples

TABLE 18-5
A manufacturer of computer disks took samples of 240 disks on 15 consecutive days. The number of disks with bad sectors was determined for each of these samples. The results are in the table that follows.
$$\begin{array} { l l l } \text { Day } & \text { Bad } & \% \text { Bad } \\\hline 1 & 9 & 0037500 \\2 & 7 & 0.029167 \\3 & 4 & 0.016667 \\4 & 6 & 0.025000 \\5 & 8 & 0.033333 \\6 & 3 & 0.012500 \\7 & 6 & 0.025000 \\8 & 10 & 0.041667 \\9 & 16 & 0.066667 \\10 & 24 & 0.100000 \\11 & 15 & 0.062500 \\12 & 9 & 0.037500 \\13 & 4 & 0.016667 \\14 & 8 & 0.033333 \\15 & 6 & 0.025000\end{array}$$
-Referring to Table 18-5, a p control chart is to be made for these data. The estimate of the standard error of the proportion of disks with bad sectors is___________ .