-2.4,9.8,22,34.2... is this arithmetic

The graph shows the distance y, in inches, a pendulum moves to the right (positive displacement) and to the left (negative displacement), for a given number of seconds x. how many seconds are required for the pendulum to move from its resting position and return? enter your answer in the box.

Whats the name of the vertical axis

The standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?