← VCE Data Analytics U3O2

Data integrity: correctness

Each value is entered in the right field and right form, and processing gives the right result. It differs from accuracy, which is how close a value is to the real world.

Part of: VCE Data Analytics - U3O2 - Analysis and Design — Module 75, QCE Digital Solutions Unit 2 — Data and Programming Techniques — Module 37

Understanding Data integrity: correctness in VCE Data Analytics U3O2

What it does: The value 16 is entered in the right type for the Age field, which meets the 'right form' part of correctness. Correctness includes processing giving the right result. A formula can run without an error and still give a wrong answer, so check the cell range. Checking a calculation means comparing the result with a known or expected result, such as a hand calculation using test data.

Common mistakes: Ava is a first name, but it was entered in the lastName field, so firstName is never set and the output is wrong. It should be firstName ← 'Ava'. Quantity was entered as text instead of a number, so price * qty cannot give a correct result. It should be qty ← 3.

Class: _____________________ · Name: _____________________ · Date: _________

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This module's key terms are also in a printable crossword (Modules 32–75) and word search (Modules 3–146).

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Each concept is reinforced from every angle — learned, then applied, then tested.

Learning

Duo

A student types the value 'Mia' into the Age field of a database. Which integrity feature does this break?

Correctness: the value is in the wrong fieldCorrectness: the value is in the right field

Matches

Mark: 95 stored in the Student Name field

↓

The value is in the wrong field, so it is incorrect. Move 95 to the Mark field.

Applying

Meanings

Term

correctness

Meaning

Each value is entered in the right field and right form, and processing gives the right result. It differs from accuracy, which is how close a value is to the real world.

Practice

=IF(SUM(B2:D2)/3=AVERAGE(B2:D2),"Correct","Check")

Testing

Gaps

SELECT FROM students

Check Answer

Spots

1lastName ← 'Ava'

2yearLevel ← 7

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Quick Questions

1. A student types the value 'Mia' into the Age field of a database. Which integrity feature does this break?

A. Correctness: the value is in the right field

B. Correctness: the value is in the wrong field ✓

Correctness means each value is entered in the right field. A name belongs in a name field, not an age field.

2. Which entry is in the right form for a field that stores Quantity as a whole number?

A. twelve

B. 12 ✓

A numeric field needs digits. Entering the word 'twelve' means the value is not in the right form, so calculations on it will fail or be wrong.

3. A spreadsheet total uses =SUM(B2:B8) but the data runs from B2 to B9. What is the result?

A. Processing is incorrect, as the total leaves out a row ✓

B. Processing is correct, as the formula has no error message

Correctness includes processing giving the right result. A formula can run without an error and still give a wrong answer, so check the cell range.

4. Which method best checks that a calculation is correct?

A. Work out the expected result by hand and compare it with the output ✓

B. Check that the formula returns some number

Checking a calculation means comparing the result with a known or expected result, such as a hand calculation using test data.

5. A shop records a pencil price as $1.50, but the real price is $1.80. The value is in the right field and form. Which feature is the issue?

A. Accuracy: it is not close to the real-world value ✓

B. Correctness: it is in the wrong field

Accuracy is how close a value is to the real world. The value is in the right field and form, so correctness is not the issue.

Match the Pairs

Phone number typed into the Email field → A correctness error: the value is in the wrong field

=SUM(B2:B9) used where AVERAGE was needed → A correctness error: processing gives the wrong result

Correct data is in the right form, so an age is stored as a number, not text → Age (integer): 16

Checking a calculation by working out a few results by hand to confirm the right result → Check: 88 + 74 + 81 = 243, and the sheet shows 243

Mark: 95 stored in the Student Name field → The value is in the wrong field, so it is incorrect. Move 95 to the Mark field.

A student scored 72 but 27 was typed. The data is called incorrect because it is not correct. → This is an accuracy error: the value does not match the real world. It is not a field or form error, so the fix is to enter 72.

Key Term

correctness

Each value is entered in the right field and right form, and processing gives the right result. It differs from accuracy, which is how close a value is to the real world.

Fill in the Blanks

1. SELECT firstName FROM students WHERE studentId = 1;

Hint: Type the field that holds a student's given name, so the value is read from the right field.

2. DECLARE yearLevel AS INTEGER

Hint: Type the data type keyword for a whole number, so the value is stored in the right form.

3. =AVERAGE(B2:D2) // mean of Ava's three marks

Hint: Type the function that calculates the mean, so the processing gives the right result.

4. =C2*D2 // total stock value of the pencils

Hint: Type the operator that multiplies price by quantity to check the calculation.

5. height ← 172 // real height is 175 cm // Correct form, but not accurate

Hint: Type the quality term for how close a value is to the real world, which is different from correctness.

Spot the Error

Question 1

A lastName ← 'Ava'

B yearLevel ← 7

C OUTPUT firstName, yearLevel

Line A — Ava is a first name, but it was entered in the lastName field, so firstName is never set and the output is wrong. It should be firstName ← 'Ava'.

Question 2

A price ← 4.50

B qty ← '3'

C total ← price * qty

D OUTPUT total

Line B — Quantity was entered as text instead of a number, so price * qty cannot give a correct result. It should be qty ← 3.

Question 3

A total ← 88 + 74 + 81

B average ← total / 2

C OUTPUT average

Line B — There are three marks, so the total must be divided by 3. Dividing by 2 gives an incorrect average, and checking the calculation by hand would show this.

Question 4

A mark1 ← 88

B mark2 ← 74

C mark3 ← 81

D total ← mark1 + mark2 + mark2

E OUTPUT total

Line D — The calculation adds mark2 twice and leaves out mark3, so the processing gives the wrong total. It should be total ← mark1 + mark2 + mark3.

Question 5

A SELECT firstName, house

B FROM students

C WHERE house > 100;

Line C — house holds text such as 'Red', so it is the wrong field to compare with the number 100. The condition should use the points field.

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