6.2.1Inquiry Process
Collecting Data in Biology — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 156 of 160
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Types of Data
Quantitative data
- Quantitative data Numerical measurements such as time, mass or volume, which can be processed with calculations and graphs.
Qualitative data
- Qualitative data Descriptive observations such as colour changes or behaviour, which add context and can explain unexpected numbers.
Raw data
- Raw data The original measurements recorded before any processing, which must be kept intact.
Sufficient data
- Sufficient data Enough values and repeats to identify a trend must be collected.
Section 2 of 5Recording Raw Data
1
Design a table before starting, with columns for the independent variable and for each repeat of the dependent variable.
2
Write the quantity and unit in the heading, such as 'Time / s', and not with each value.
3
Record every value to the same number of decimal places, matching the resolution of the instrument.
4
Include the uncertainty of each measurement, either in the heading or in a separate column.
5
Add notes on observations and on any problems, such as spilled solution, to the table or beside it.
| Temperature / °C (±0.5) | Trial 1 time / s (±0.2) | Trial 2 time / s (±0.2) | Trial 3 time / s (±0.2) |
|---|---|---|---|
| 20 | 41.2 | 40.8 | 41.5 |
| 30 | 28.4 | 27.9 | 28.1 |
Section 3 of 5Good Practice in Collection
Good Practice in Collection
Repeats
- Repeats Measurements are repeated under identical conditions to allow a mean and to spot an anomaly.
Random sampling
- Random sampling In fieldwork, sample positions are chosen with random numbers so that no bias occurs.
Anomalies
- Anomalies An unexpected value is recorded and flagged, and is not removed from the raw data without a reason.
Recording promptly
- Recording promptly Data are written down at the time, not remembered, to prevent mistakes.
Section 4 of 5Worked Example
Question
- Three students time a colour change with a stopwatch reading to 0.01 s and obtain 12.4, 12.6 and 12.5 s.
- What precision should the values be recorded to, and what is the mean?
- Human reaction time in starting and stopping the watch is about 0.2 s, so recording to 0.1 s is realistic even though the display shows 0.01 s.
- Mean = (12.4 + 12.6 + 12.5) ÷ 3 = 37.5 ÷ 3 = 12.5 s.
- The range is 12.6 − 12.4 = 0.2 s, which is consistent with the reaction-time uncertainty.
Answer The mean is 12.5 s (±0.2 s), recorded to one decimal place.
Section 5 of 5Exam Checklist & Tips
6.2.1 – Key Points for the Exam
- Raw data Original recorded measurements before any processing.
- Qualitative data Descriptive, non-numerical observations.
- Anomaly A result that does not fit the pattern of the other data.
- Precision The closeness of repeated measurements to each other.
Common Mistakes
- Giving more decimal places than the instrument or method can justify.
- Writing units next to each number instead of in the table heading.
- Deleting an anomalous result from the raw data.
- Collecting only quantitative data and ignoring useful observations.
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