For this case we have a function of the form:
y = A * (b) ^ t
Where,
A: initial amount
b: decrease rate
t: time
We must find the values of A and b.
For this, we evaluate the following points:
(0, 30):
30 = A * (b) ^ 0
30 = A * 1
30 = A
(1, 28.5):
28.5 = 30 * (b) ^ 1
28.5 = 30 * b
b = 28.5 / 30
b = 0.95
Answer:
the decay factor of the data is:
b = 0.95