IB Biology HL 2, How do you do the calculation of uncertainty for independent and dependent variables obtaiend without a measuring tool/apparatus?

Question

For an essay assessment in biology, I need to calculate my uncertainty for my independent and dependent variable. However, my independent variable is vocal technique (mixed voice, head voice, chest voice, etc) and my dependent variable is breaths per minute. How do I calculate the uncertainty for these variables if I did not measure them (I counted breaths per minute off of a graph, data required from a respiratory belt the experimenter sang into).

1. Edit: The respiratory belt gas sensor used is +/- 4 kPa, however I still was counting the breath spikes on the graph itself.

Answer 1

Hello, I know this question was already answered but I am going to disagree with the previous answer. Since the number of breaths is a count, it will not have uncertainty since counts of something are exact. You would have to come up with a consistent way to determine what is considered a "breath" though. If a breath is cutoff halfway at the end of a minute, do you count it?

Also, your IV is not ideal. It is hard to reproduce since there are so many uncontrollable variables between different people singing. Also, are you using only 1 person for this experiment? If so, this also presents a problem since a sample size of 1 person is not very good.

Answer 2

For The Dependent Variable (Breaths Per Minute):

Use ±1 breath for uncertainty due to potential miscounting on the graph.

Respiratory belt uncertainty (±4 kPa) likely doesn’t directly affect breath counts but can be noted in limitations.

Example: If you counted 15 breaths, report 15±1 BPM.

For The Independent Variable (Vocal Technique):

It’s categorical, so no numerical uncertainty applies.

Mention variability in performance consistency as a qualitative uncertainty in your discussion.