Does rounding a number change whether a math sequence spirals into chaos? Iterative processes repeat the same equation over and over. A tiny change in precision can shift the outcome from a steady pattern to total unpredictability.
You use the equation x(n+1) = rx(n)(1-x(n)) in a spreadsheet. You test different values of the constant r from 2.70 to 3.70. For each value you run 26 rounds at precision levels of 2, 3, 4, and 15 decimal places.
Some constants produce sequences that settle on one number. Others make the sequence alternate between two values. Still others create chaos with no pattern at all. You discover that for certain constants, just changing the rounding level switches the outcome from alternating to steady.
Hypothesis
The hypothesis is that the constant used will have a great effect on the type of sequence that results, and that precision will have a distinct effect on the outcomes.
When you feed a result back into the same equation over and over, small differences can compound. In the logistic equation x(n+1) = rx(n)(1-x(n)), some constants produce sequences that settle on one number, while others create chaos with no pattern at all. Even a tiny change in precision can shift the outcome from a steady pattern to total unpredictability.
Tiny changes in a starting point can cause wildly different results — and precision itself counts as a starting condition. When you run the iterative equation x(n+1) = rx(n)(1-x(n)) at different rounding levels, something striking happens: just changing the decimal precision, without touching the math itself, can switch the outcome from alternating to steady. Across 26 rounds with constants r ranging from 2.70 to 3.70, some values settle on one number, others alternate between two, and still others spiral into total unpredictability. That shift from order to chaos driven by rounding alone — not by any change in the equation — is chaos theory made visible in a spreadsheet.
When you run the equation x(n+1) = rx(n)(1-x(n)) for 26 rounds at 2, 3, 4, and 15 decimal places, the number of digits you carry through each step determines which long-term behavior emerges. For certain constants, a sequence might settle on one number at 15 decimal places but alternate between two values at just 2. That means changing the rounding level alone can switch the outcome from alternating to steady — not because the math changed, but because the exact digits you kept did.
Method & Materials
You will compare outcomes for different values of the constant r and different levels of precision for the iterative process x(n+1) = rx(n)(1-x(n)). Each process will be repeated for 26 iterations, starting with x(0) = 0.5.
You will need Microsoft Excel to calculate the iterations.
MEL Math — hands-on math experiment kits delivered monthly — makes abstract concepts tangible. (Affiliate link)
The experiment revealed that the constant used had a great effect on the type of sequence that resulted, and that precision had a distinct effect on the outcomes. For some constants, changing the level of rounding had such a strong effect that the same sequence would either bifurcate or converge, depending on the precision.
Why do this project?
This science project is so interesting because it reveals how chaos appears in iterative processes with differing levels of precision.
Also Consider
Experiment variations to consider include testing different constants and different levels of precision for the iterative process.
Full project details
Additional information and source material for this project are available below.