The mode is the middle value.
Write the numbers out from smallest to largest:
2.0, 2.6, 2.6, 2.9, 3.2, 3.5, 4.1, 4.1,4.1,5.2,5.6,7.2,7.7,7.8
There are 14 numbers, so the mode would be between the 7th and 8th numbers.
To find this, add the 7th and 8th numbers together and divide by 2.
4.1 + 4.1 = 8.2 / 2 = 4.1.
The mode is 4.1
