ChemistryChapter 16: Empirical Data Collection and Analysis
Reliability, Validity, and Graphs
Reliable means repeats sit close (precision).
Definition
Reliable means repeats sit close (precision). Valid means you measured what you claimed (the right variable, fair test). A graph is part of the argument: labelled axes with units, a sensible scale, and a line only if the in-between values make sense.
Relationship
- reliable = close repeats
- valid = right measurement
Overview
Numbers, then the picture:
Reliable and Valid
Three titres within 0.1 cm^3 are precise. If you used the wrong indicator, they can still be invalid. An outlier: check the burette, do not hide it. Accuracy is closeness to the true value (a standard).
Examples Concordant titres named · Wrong end-point colour · Zero error on a balance
Tables and Graphs
Tables need quantity and unit in the heading, not on every cell. Plot the independent variable on x. A bar chart is for categories; a line is for continuous x (time, temperature). Circle the anomaly.
Examples Time vs temperature cooling · Do not join bar tops as a 'line' without thought · Best-fit is not join-the-dots through a wild point
Explanation
Scientific notation and prefixes were earlier pages. A result 1.20 x 10^-3 mol is three significant figures if those digits were measured.
In simple words
A computer graph is not automatically valid. Garbage in, a pretty scatter out.
Key points
- reliable = close repeats
- valid = right measurement
- repeats
- right method
Quick revision
Revision Zone
Review the key facts, formulas and checks before you move on.Reliability, Validity, and Graphs
Sticky Notes · Quick Revision
Core Idea
- Reliable means repeats sit close (precision).
Key Points
- reliable = close repeats
- valid = right measurement
Simple Check
- Explain reliability, validity, and graphs in your own words and connect it to one chapter example.
How to Answer
- Define the idea, show the main rule or evidence, apply it, and check the final statement.
Common Mistake
- A computer graph is not automatically valid. Garbage in, a pretty scatter out.
FBISE Exam Tip
- Use the exact term, show working where needed, and include units or labelled evidence.
60-second revision
- reliable = close repeats
- valid = right measurement
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