← VCE Data Analytics U3O2

Data integrity: reasonableness

Data is reasonable when its values are sensible and plausible for what they describe. An age of 250 fails a reasonableness check on a range, such as 0 to 120.

Part of: VCE Data Analytics - U3O2 - Analysis and Design — Module 76, QCE Digital Solutions Unit 2 — Data and Programming Techniques — Module 38

Understanding Data integrity: reasonableness in VCE Data Analytics U3O2

What it does: The code accepts a mark only when it lies inside the plausible range of 0 to 100, which is a range-based reasonableness check. 16 lies within 0 to 120 and is sensible for a student, so it passes the check. A number can be valid and still be unreasonable. No person is 250 years old, so the value fails a reasonableness check. Reasonableness asks whether a value makes sense in the real world for the thing it describes, not just whether it is stored correctly. 34 sits inside the range 0 to 120. A negative age is outside the range, so it fails.

Common mistakes: The lower limit of the range must be 0, not 200. With a lower limit above the upper limit of 120, no age could ever pass the reasonableness check. It should be lo ← 0. This branch runs when the age is inside the range 0 to 120, so the value is reasonable. The output should be OUTPUT 'Reasonable'.

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This module's key terms are also in a printable crossword (Modules 76–146) and word search (Modules 3–146).

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Learning
Duo
A student's age is recorded as 250 in a dataset. Is this value reasonable?
No, it is not plausible for a person's ageYes, it is a valid number so it is reasonable
Matches
Range check for age: 0 to 1000
↓
The range is too wide to be a useful reasonableness check, because an age of 250 would still be accepted. A sensible upper limit is about 120.
Applying
Meanings
Term
reasonableness
Meaning
Data is reasonable when its values are sensible and plausible for what they describe. An age of 250 fails a reasonableness check on a range, such as 0 to 120.
Practice
INPUT age
Testing
Gaps
SELECT name FROM people WHERE age 120;
Check Answer
Spots
1lo ← 200
2hi ← 120

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Quick Questions

1. A student's age is recorded as 250 in a dataset. Is this value reasonable?
A. No, it is not plausible for a person's age ✓
B. Yes, it is a valid number so it is reasonable
A number can be valid and still be unreasonable. No person is 250 years old, so the value fails a reasonableness check.
2. Which best describes data integrity: reasonableness?
A. Values are stored in the correct data type only
B. Values are sensible and plausible for what they describe ✓
Reasonableness asks whether a value makes sense in the real world for the thing it describes, not just whether it is stored correctly.
3. A reasonableness check on an age field uses a range of 0 to 120. Which value passes?
A. -5
B. 34 ✓
34 sits inside the range 0 to 120. A negative age is outside the range, so it fails.
4. Which value fails a reasonableness check on a range of 0 to 100 for a test percentage?
A. 135 ✓
B. 87
A percentage cannot be above 100, so 135 is outside the range and fails the check. 87 is within the range.
5. What does a range check do when testing for reasonableness?
A. Tests whether a value lies between a minimum and a maximum ✓
B. Tests whether a value is typed in capital letters
A range check compares a value with set lower and upper limits, such as 0 to 120 for age, to catch implausible values.

Match the Pairs

IF age < 0 OR age > 120 THEN reject → A range-based reasonableness check that rejects any age outside 0 to 120
age = 250 → An unreasonable value because no person could be 250 years old
A reasonableness check tests whether a value sits inside a sensible range → IF mark >= 0 AND mark <= 100 THEN accept
A plausible age passes a reasonableness check on a range of 0 to 120 → age = 16
Range check for age: 0 to 1000 → The range is too wide to be a useful reasonableness check, because an age of 250 would still be accepted. A sensible upper limit is about 120.
age = -5 passes because it is a number → Being a valid number does not make a value reasonable. A negative age is implausible and should fail the check.

Key Term

reasonableness
Data is reasonable when its values are sensible and plausible for what they describe. An age of 250 fails a reasonableness check on a range, such as 0 to 120.

Fill in the Blanks

1. SELECT name FROM people WHERE age > 120;
Hint: Type the comparison operator that finds ages above the upper limit of the range.
2. =IF(AND(B2>=0,B2<=120),"OK","Check")
Hint: Type the function that is true only when both range conditions are met.
3. IF age < 0 OR age > 120 THEN DISPLAY "Age not reasonable" END IF
Hint: Type the logical operator that flags a value outside either end of the range.
4. SELECT * FROM people WHERE age BETWEEN 0 AND 120;
Hint: Type the SQL keyword that tests whether a value lies within a range.
5. =COUNTIF(B2:B30,">120")
Hint: Type the function that counts cells meeting a condition, to find unreasonable ages.

Spot the Error

Question 1
A lo ← 200
B hi ← 120
C IF age >= lo AND age <= hi
D OUTPUT 'Reasonable'
Line A — The lower limit of the range must be 0, not 200. With a lower limit above the upper limit of 120, no age could ever pass the reasonableness check. It should be lo ← 0.
Question 2
A INPUT age
B IF age >= 0 AND age <= 120
C OUTPUT 'Not reasonable'
D ELSE
E OUTPUT 'Not reasonable'
Line C — This branch runs when the age is inside the range 0 to 120, so the value is reasonable. The output should be OUTPUT 'Reasonable'.
Question 3
A age ← 250
B valid ← FALSE
C IF age >= 0 AND age <= 120
D valid ← FALSE
E OUTPUT valid
Line D — When the age is inside the range 0 to 120 the value is reasonable, so valid must be set to TRUE. It should be valid ← TRUE.
Question 4
A hi ← 1200
B lo ← 0
C IF age < lo OR age > hi
D OUTPUT 'Check age'
Line A — An upper limit of 1200 is not a plausible human age, so an age of 250 would wrongly pass the check. The upper limit should be hi ← 120.
Question 5
A INPUT age
B valid ← TRUE
C IF age < 0 AND age > 120
D valid ← FALSE
E OUTPUT valid
Line C — No age can be below 0 and above 120 at the same time, so the condition is never true and an age of 250 would pass. It needs OR: IF age < 0 OR age > 120.

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