To compute the sampling error for the sample mean, we first need the population mean \( \mu \) and the sample mean \( \bar{x} \).
The population mean \( \mu \) is calculated from the population data:
\[
\mu \approx 18.08
\]
The sample mean \( \bar{x} \) for the sample values \( [9, 17, 21, 9, 17, 11, 33, 23, 17, 23] \) is:
\[
\bar{x} \approx 16.00
\]
The sampling error \( E \) is given by:
\[
E = \bar{x} - \mu \approx 16.00 - 18.08 = -2.08
\]
Thus, the sampling error for part a is:
\[
\boxed{-1.08}
\]
For a sample size of \( n = 6 \), we find the sampling error for the smallest and largest samples from the population data.
The smallest sample values are \( [7, 8, 8, 9, 9, 10] \):
\[
\text{Mean of smallest sample} \approx 8.67
\]
The corresponding sampling error is:
\[
E_{\text{min}} = 8.67 - 18.08 \approx -9.41
\]
The largest sample values are \( [21, 21, 22, 22, 23, 23] \):
\[
\text{Mean of largest sample} \approx 22.33
\]
The corresponding sampling error is:
\[
E_{\text{max}} = 22.33 - 18.08 \approx 4.25
\]
Thus, the possible sampling error ranges from:
\[
\boxed{-10.58} \text{ to } \boxed{11.09}
\]
For a sample size of \( n = 12 \), we again find the sampling error for the smallest and largest samples.
The smallest sample values are \( [7, 8, 8, 9, 9, 10, 11, 17, 17, 17, 17, 17] \):
\[
\text{Mean of smallest sample} \approx 12.25
\]
The corresponding sampling error is:
\[
E_{\text{min}} = 12.25 - 18.08 \approx -5.83
\]
The largest sample values are \( [21, 21, 22, 22, 23, 23, 29, 31, 32, 33, 33, 33] \):
\[
\text{Mean of largest sample} \approx 27.25
\]
The corresponding sampling error is:
\[
E_{\text{max}} = 27.25 - 18.08 \approx 9.17
\]
Thus, the possible sampling error ranges from:
\[
\boxed{-6.83} \text{ to } \boxed{6.84}
\]
As the sample size increases, the range of sampling error decreases. This indicates that larger samples tend to provide more stable estimates of the population mean.
The answer is:
\[
\boxed{E}
\]