Radioactive decay and half life?

[kraphysics]

Homework Statement

I have some data for "Activity(Bq * 10^4)" and "time". I have already found the half life and everything but I can't seem to see any sources of error in the data

Homework Equations

I need sources of error.

The Attempt at a Solution

I said, the half life matches the activity well but then as the time increases, the predictions using the formula N= No((1/2)^t/t(1/2)) and half life are true for some points but later it gets slightly off. I don't know why this happens..

 

[HallsofIvy]

Homework Statement

I have some data for "Activity(Bq * 10^4)" and "time".

How can you expect anyone to understand what you mean by that?

I have already found the half life and everything but I can't seem to see any sources of error in the data

Homework Equations

I need sources of error.

The Attempt at a Solution

I said, the half life matches the activity well but then as the time increases, the predictions using the formula N= No((1/2)^t/t(1/2)) and half life are true for some points but later it gets slightly off. I don't know why this happens..

 

[kraphysics]

How can you expect anyone to understand what you mean by that?

Time (min) Activity (Bq x10^4)
0 8.00
10 5.04
20 3.17
30 2.01
40 1.26
50 0.790
60 0.490
70 0.320
80 0.195
90 0.128

From graphing the data, I have found half life to be 15.0 minutes.