Note: You missed to add the dot plots chart. As I found the chart after a little research. Thus, I am attaching it and based on that dot plot chart I am solving the question which anyways would clear you concept.
Answer:
'There are about 2 more students in each class at Oak Middle School than at Poplar Middle School' is the correct statement.
Step-by-step explanation:
From the diagram, it is clear that
The data set containing Poplar Middle School:
20 20 20 21 21 21 21 21 22 22 22 22 22 22 22 23 23 23 23 24
The mean of a data set is the sum of the terms divided by the total number of terms. Using math notation we have:



The data set containing Oak Middle School:
20 21 21 22 22 23 23 23 23 24 24 24 25 25 26 26 27 27 28 29
The mean of a data set is the sum of the terms divided by the total number of terms. Using math notation we have:


So, the difference in mean will be:

Therefore, 'there are about 2 more students in each class at Oak Middle School than at Poplar Middle School' is the correct statement.