Reaction time practicals and data skills

Homeostasis and response • The human nervous system

Flashcards

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Give three examples of control variables for the ruler-drop test.

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Lighting level, posture and which hand is used remain constant between trials.

Key concepts

What you'll likely be quizzed about

Ruler-drop reaction time practical (method and rationale)

A subject places the thumb and forefinger at the 0 cm mark while a tester holds a ruler at the 30 cm mark and releases it without warning; the distance caught gives a measure of reaction time because greater distance indicates a longer fall and therefore a longer reaction interval . Randomisation of drop timing prevents anticipation and multiple repeats improve reliability; conversion charts or the equation for free fall translate distance into seconds for comparison across conditions. Limiting factors include tester cues, practice effects, participant fatigue and environmental distractions, all of which change measured reaction times.

Planning an investigation into a factor that affects reaction time

A clear aim states the independent variable (factor to change), the dependent variable (reaction time converted to seconds) and controlled variables (lighting, posture, hand used, practice trials). The design includes randomised drop timing, at least three repeats per condition to calculate a mean, and swapping roles to check reproducibility . Safety and ethics include informed consent, avoidance of hazardous stimuli and the option to stop if the participant feels unwell; reporting includes raw data, means and an account of anomalies.

Translating numerical data to graphs and back

Quantitative reaction-time data appear as distances or times and require correct graph choice: line graphs or scatter plots for continuous independent variables, bar charts for discrete categories. Axes must include units and appropriate scales; plotting mean values with error bars clarifies variation and precision . A plotted trend line reveals the nature of the relationship; the slope or curvature indicates whether reaction time increases, decreases or remains stable as the factor changes.

Extracting and interpreting data from graphs, tables and charts

A graph provides visual evidence of trends, correlations and outliers; reading values from axes and calculating differences or percentage changes allows quantitative interpretation. Identification of anomalous results prompts re-checking for measurement error or procedural variation and informs whether to exclude an anomaly when drawing a trend line . Correlation seen on a plot does not prove causation; additional controls and repeated testing determine whether a factor causes the change in reaction time rather than correlates with it .

Key notes

Important points to keep in mind

The ruler-drop method converts caught distance to time using a conversion chart or the free-fall equation; always record units and significant figures .

Randomise drop timing to prevent anticipation and reduce systematic bias .

Collect at least three repeats per condition and calculate a mean to improve reliability.

Control environmental and participant variables such as lighting, posture and hand used.

Plot numerical data using the appropriate graph type: line or scatter for continuous variables, bar chart for categories .

Label axes clearly with units and choose a scale that uses most of the graph area.

Spot anomalies early and check raw data and method notes before deciding whether to exclude them from trend analysis .

Distinguish correlation from causation; additional controlled tests are necessary to prove cause-effect relationships .

Report both central values (mean) and variation (range or error bars) to show precision and spread.

State limitations and possible confounding variables when drawing conclusions from reaction-time experiments.