The accompanying data contains the monthly retail sales ($millions) of a large country's women's clothing stores for 70 months. A sample taken from this population to estimate the average sales in this time period is shown below. Complete parts a through d below.

2,892	2,328	3,133	2,724	2,554	2,997	2,671	2,409	2,906
2,839	2,820	3,146	2,436	2,686	3,177	3,071	2,713	2,466
3,089	3,125	3,024	2,727	2,412	3,077	2,443

c. How much sampling error is present in this sample?