Question 5 from Practice Test for Inferential Statistics (Standard Error)

In this question, we are given Sample Means as the data set (which I understand is a sampling distribution of the mean) and asked to calculate the Standard Error (SE). My understanding is that SE for a sampling distribution is just the Standard Deviation (SD) of that sampling distribution (00:30 mark in the video). So we need to calculate the SD which is 2620.60.

In the solution, however, 2620.60 is divided by the square root of the sample size to get the SE. That means 2620.6 is being considered as the population SD. But it is actually the SD of the sampling distribution.