Practice neco data_processing 2024 Past Questions

Question 1 View Details

Consider a relation R(A,B,C,D) with functional dependencies \(A \rightarrow B\), \(BC \rightarrow D\), and \(D \rightarrow A\). Determine the highest normal form (1NF, 2NF, 3NF or BCNF) that R satisfies.

A. Second Normal Form (2NF)

Correct B. Third Normal Form (3NF)

C. First Normal Form (1NF)

D. Boyce-Codd Normal Form (BCNF)

Correct Answer: B

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Question 2 View Details

A file can be accessed by three methods: sequential (average access time 12 ms), indexed (8 ms) and direct (4 ms). The probabilities of using these methods are 0.5, 0.3 and 0.2 respectively. The system requires an overall average access time of at most 7 ms. If the relative ratio between sequential and indexed accesses must remain the same, what minimum proportion of direct‑access requests is needed to meet the requirement? Express your answer as a decimal rounded to two places.

A. 0.45

Correct B. 0.54

C. 0.64

D. 0.50

Correct Answer: B

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Question 3 View Details

Given the Boolean function \(F(A,B,C,D) = \Sigma m(1,3,4,7,11,12,13,15) + \Sigma d(0,2,5,9)\), find a minimal sum‑of‑products expression and state the total number of literals in that expression.

A. F = \\overline{A}D + \\overline{B}D + B\\overline{C} + AB\\overline{D}, 9 literals

Correct B. F = \overline{A}D + \overline{B}D + B\overline{C} + ABD, 9 literals

C. F = \\overline{A}D + B\\overline{C} + ABD, 7 literals

D. F = \\overline{A}D + \\overline{B}D + BC + ABD, 8 literals

Correct Answer: B

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Question 4 View Details

An organization requires passwords of length 8 characters. Each character can be an uppercase letter (26), a lowercase letter (26), a digit (10) or a special symbol (12). The policy mandates that a password contain at least one uppercase letter, one digit and one special symbol. \n\n(a) How many distinct passwords satisfy the policy? \n\n(b) If an attacker can test \(10^{6}\) passwords per second and the average time to crack a password is half the size of the key‑space, does the policy meet the security standard that the average cracking time must exceed 5 years? \n\n(c) Briefly discuss the ethical issue of storing passwords in plain text.

A. (a) Approximately 4.31×10^{13} passwords. (b) No - average cracking time ≈2.5 years, far below the 5‑year standard. (c) Storing passwords in plain text is ethical because it allows users to retrieve forgotten passwords easily.

Correct B. (a) Approximately 4.31×10^{14} passwords. (b) Yes - average cracking time ≈6.8 years, which exceeds 5 years. (c) Storing passwords in plain text is unethical because it breaches confidentiality and puts users at risk; passwords should be stored as salted hashes.

C. (a) Approximately 5.0×10^{14} passwords. (b) Yes - average cracking time ≈5.2 years, which barely meets the 5‑year requirement. (c) Storing passwords in plain text is permissible as long as users are informed, though hashing is recommended for convenience.

D. (a) Approximately 3.2×10^{14} passwords. (b) No - average cracking time ≈4.2 years, which is less than 5 years. (c) Storing passwords in plain text is acceptable if the system uses strong firewalls; it does not pose a major ethical concern.

Correct Answer: B

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Question 5 View Details

A data set consists of the nine values 12, 15, 18, 22, 27, 33, 40, 58 and 120. After discarding the highest outlier (120), compute the mean and the median of the remaining values. Give your answers to three decimal places for the mean.

A. Mean = 28.125, Median = 27

B. Mean = 30.125, Median = 24.5

C. Mean = 27.500, Median = 24.5

Correct D. Mean = 28.125, Median = 24.5

Correct Answer: D

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Question 6 View Details

A table shows the monthly sales (in units) of three products: Product A - 120 units, Product B - 95 units, Product C - 130 units. Which type of chart is most suitable for comparing the sales of the three products?

A. Line graph

Correct B. Bar chart

C. Scatter plot

D. Pie chart

Correct Answer: B

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Question 7 View Details

A data set consists of the values 120, 85, 95, 110 and 130. During the validation stage any value less than 100 is discarded. After validation, the average of the remaining values is calculated and then rounded to the nearest whole number. What is the rounded average, and which stage of the data‑processing cycle produces this average?

A. 130, Analysis

B. 120, Interpretation

C. 115, Collection

Correct D. 120, Processing

Correct Answer: D

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Question 8 View Details

In a spreadsheet the following data are entered: \begin{tabular}{lcc} Product & Unit Price (\(\text{₦}\)) & Quantity Sold \\ P1 & 2500 & 40 \\ P2 & 1800 & 55 \\ P3 & 3200 & 30 \\ P4 & 1500 & 70 \\ \end{tabular} The total sales for each product are computed as \(\text{Unit Price}\times\text{Quantity Sold}\). A discount of 10\% is applied to the total sales of any product whose quantity sold exceeds 50 units. Calculate the total revenue after all applicable discounts.

Correct A. 379600

B. 389800

C. 360000

D. 400000

Correct Answer: A

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Question 9 View Details

Given the Boolean function \(F = (A + \overline{B})\cdot(\overline{A} + B + C)\), simplify the expression to a minimal sum‑of‑products form and state the minimum number of two‑input NAND gates required to implement the simplified function.

A. AB + \\overline{A}B + \\overline{B}C; 9

Correct B. AB + \overline{A}\overline{B} + \overline{B}C; 10

C. A\\overline{B} + \\overline{A}\\overline{B} + \\overline{B}C; 12

D. AB + \\overline{A}\\overline{B} + \\overline{C}B; 10

Correct Answer: B

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Question 10 View Details

A circuit consists of a two‑input NAND gate whose inputs are \(A\) and \(B\). The output of this NAND gate is connected to both inputs of a second NAND gate, whose output is the circuit output \(Z\). Determine the Boolean expression for \(Z\) in terms of \(A\) and \(B\) and simplify it.

A. Z = A + B

Correct B. Z = AB

C. Z = A ⊕ B

D. Z = A'B

Correct Answer: B

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Question 11 View Details

A file contains \(5{,}000\) records, each \(250\) bytes long. The storage medium uses blocks of \(1{,}024\) bytes. Compare the total storage required (in bytes) for the following file‑organization methods and state which method uses the least storage:\n\n1. Sequential organization (records stored consecutively).\n\n2. Indexed sequential organization, where an index block stores a \(4\)-byte pointer for each data block.\n\n3. Direct (hashed) organization, assuming each record occupies its own block and \(5\)% of the records suffer a collision, each requiring an additional overflow block.\n\nAssume that any partially‑filled block still occupies a full block. Provide the storage amounts for each method and identify the method with minimum storage.

A. Direct organization (1,312,500 bytes)

B. Indexed sequential organization (1,260,800 bytes)

Correct C. Sequential organization (1,250,304 bytes)

D. Sequential organization (1,300,000 bytes)

Correct Answer: C

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Question 12 View Details

A company records monthly sales (in Naira) of three products A, B and C for a full year.\n\nProduct A sales (Jan-Dec): 50 000, 55 000, 60 000, 65 000, 70 000, 75 000, 80 000, 85 000, 90 000, 95 000, 100 000, 105 000.\n\nProduct B sales are known for the first six months only: Jan = 40 000, Feb = 42 000, Mar = 44 000, Apr = 46 000, May = 48 000, Jun = 50 000. The sales for July-December are not given.\n\nThe total annual sales of product C are 300 000 Naira, and product C sales are the same each month. The total annual sales of all three products combined are 1 800 000 Naira.\n\n(a) Determine the monthly sales of product B for July-December.\n(b) For each quarter (Q1: Jan-Mar, Q2: Apr-Jun, Q3: Jul-Sep, Q4: Oct-Dec) compute the percentage contribution of product B to the total sales of that quarter.\n(c) Identify the quarter in which product B contributed the greatest percentage to the quarter's total sales, and give that percentage rounded to two decimal places.

Correct A. July-December B sales = 50,000 Naira each; Quarter 1, 34.43\%

B. July-December B sales = 50,000 Naira each; Quarter 1, 32.00\%

C. July-December B sales = 55,000 Naira each; Quarter 1, 38.75\%

D. July-December B sales = 45,000 Naira each; Quarter 1, 30.12\%

Correct Answer: A

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Question 13 View Details

Consider the relation STUDENT with attributes (StudentID, Name, Dept, Advisor, AdvisorPhone) and the following functional dependencies:\n\n1. StudentID \(\rightarrow\) Name, Dept, Advisor\n2. Advisor \(\rightarrow\) AdvisorPhone\n3. Dept \(\rightarrow\) Advisor\n\n(a) Determine the highest normal form (up to 3NF) that the STUDENT relation satisfies.\n(b) If it is not in 3NF, decompose the relation into a set of relations that are in 3NF while preserving the dependencies.

A. The STUDENT relation is in 3NF. Decomposition into 3NF: STUDENT1(StudentID, Name, Dept) and ADVISOR(Advisor, AdvisorPhone).

Correct B. The STUDENT relation is in 2NF (not 3NF). Decomposition into 3NF: STUDENT1(StudentID, Name, Dept, Advisor) and ADVISOR(Advisor, AdvisorPhone).

C. The STUDENT relation is in 2NF (not 3NF). Decomposition into 3NF: STUDENT1(StudentID, Name, Dept, AdvisorPhone) and ADVISOR(Advisor, AdvisorPhone).

D. The STUDENT relation is in 1NF only. Decomposition into 3NF: STUDENT1(StudentID, Name, Dept, Advisor) and ADVISOR(Advisor, AdvisorPhone).

Correct Answer: B

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Question 14 View Details

The following set of seven test scores (in marks) was obtained: 12, 15, 9, 20, 14, 11, 13. Arrange the scores in ascending order and determine the median score.

Correct A. 13

B. 14

C. 12

D. 11

Correct Answer: A

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Question 15 View Details

A company has identified three independent security threats with the following inherent risk scores (on a scale from 0 to 1):\n\n- Threat A: 0.8\n- Threat B: 0.6\n- Threat C: 0.4\n\nThree security controls are available:\n\n- Control X reduces Threat A by 45 % (effectiveness = 0.45).\n- Control Y reduces Threat B by 55 % (effectiveness = 0.55).\n- Control Z reduces Threat C by 80 % (effectiveness = 0.80).\n\nOnly two controls can be implemented because of budget limits. The residual risk for a threat after a control is applied is calculated as\n\[\n\text{Residual Risk}= \text{Inherent Risk}\times (1-\text{Effectiveness}).\n\]\nDetermine which pair of controls should be implemented to achieve the lowest total residual risk (sum of residual risks for all three threats). State the chosen controls and the resulting total residual risk (rounded to three decimal places).

Correct A. Implement Controls X and Y; total residual risk = 1.110

B. Implement Controls Y and Z; total residual risk = 1.150

C. Implement Controls X and Z; total residual risk = 1.120

D. Implement Controls X and Y; total residual risk = 1.130

Correct Answer: A

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Question 16 View Details

A data file contains \(250\) records, each record has \(12\) fields. Each field occupies \(0.8\) kilobytes. What is the total size of the file in megabytes? (Assume \(1\) megabyte = \(1000\) kilobytes.)

A. 2.8 MB

Correct B. 2.4 MB

C. 3.0 MB

D. 2.0 MB

Correct Answer: B

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Question 17 View Details

A small business purchases a computer for \(150{,}000\) naira. The computer depreciates straight‑line over 5 years with zero salvage value. Each transaction handled by the computer saves \(12\) minutes of employee time. The business processes \(150\) transactions per month, and the employee's wage is \(1{,}200\) naira per hour. Assuming the depreciation expense is incurred each month, after how many complete months will the cumulative net savings equal or exceed the purchase cost of the computer?

A. 6 months

Correct B. 5 months

C. 8 months

D. 4 months

Correct Answer: B

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Question 18 View Details

A file of \(10{,}200\) bytes is to be stored on a disk whose block size is \(4{,}096\) bytes.\n\n(i) If the file is stored using contiguous allocation, how many blocks are required and what is the total storage used (including any internal fragmentation)?\n\n(ii) If the file is stored using linked allocation where each block requires a separate \(64\)-byte pointer block, how many data blocks are required and what is the total storage used (including pointer blocks and internal fragmentation)?\n\nState which allocation method uses less total storage.

Correct A. Contiguous allocation uses less total storage (12,288 bytes vs 12,480 bytes for linked).

B. Linked allocation uses less total storage (12,288 bytes vs 12,480 bytes for contiguous).

C. Contiguous allocation uses less total storage (12,480 bytes vs 12,288 bytes for linked).

D. Both allocation methods use the same total storage (12,384 bytes).

Correct Answer: A

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Question 19 View Details

In a data processing system the average times required for each stage of a batch are: Input \(4\) min, Validation \(2\) min, Processing \(5\) min, Output \(3\) min, Storage \(1\) min. If the system processes \(8\) batches sequentially, what is the total time required to complete all batches, and which stage accounts for the greatest proportion of the total processing time?

A. Total time = 120 minutes; the Input stage accounts for the greatest proportion (≈33 %).

B. Total time = 130 minutes; the Processing stage accounts for the greatest proportion (≈35 %).

Correct C. Total time = 120 minutes; the Processing stage accounts for the greatest proportion (≈33 %).

D. Total time = 115 minutes; the Validation stage accounts for the greatest proportion (≈27 %).

Correct Answer: C

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Question 20 View Details

A data file stores \(1{,}200\) integer values, each occupying \(2\) bytes. What is the size of the file in kilobytes? (Use \(1\) kilobyte = \(1{,}024\) bytes and give your answer to two decimal places.)

A. 2.33 KB

B. 2.40 KB

C. 2.35 KB

Correct D. 2.34 KB

Correct Answer: D

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Question 21 View Details

A small business is evaluating three security controls. Control A (firewall) costs \(\text{₦}150{,}000\) and reduces the overall risk by 60\%. Control B (encryption) costs \(\text{₦}120{,}000\) and reduces risk by 50\%. Control C (IDS) costs \(\text{₦}200{,}000\) and reduces risk by 40\%. The initial risk level is 100 units and risk reductions are multiplicative, i.e. after applying a control the remaining risk = previous risk \(\times (1-\text{reduction})\). The business wants the final risk to be at most 20 units. Which combination of controls meets the target with the minimum total cost? State the total cost and the controls chosen.

A. ₦350,000 (Controls A and C)

B. ₦470,000 (Controls A, B, and C)

C. ₦320,000 (Controls B and C)

Correct D. ₦270,000 (Controls A and B)

Correct Answer: D

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Question 22 View Details

In a batch‑processing system the data‑processing cycle consists of four stages: Input (4 min), Processing (12 min), Output (5 min) and Storage (3 min). Input and Output stages may be performed simultaneously on different records, but Processing and Storage cannot overlap with any other stage. If five records are processed sequentially through the cycle, what is the total time required to complete all five records?

A. 84 minutes

B. 96 minutes

C. 104 minutes

Correct D. 92 minutes

Correct Answer: D

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Question 23 View Details

A database uses three file‑organization methods. For a particular query the probabilities of accessing a record via each method are: Sequential 0.5, Indexed‑Sequential 0.3, Direct 0.2. Their average access times are 8 ms, 5 ms and 2 ms respectively. (a) Compute the expected access time for the query. (b) If a new indexing scheme reduces the Indexed‑Sequential access time by 20 % (i.e. to 4 ms) while the other times stay unchanged, what is the new expected access time? Give both results in milliseconds.

Correct A. 5.9 ms (original), 5.6 ms (after improvement)

B. 5.8 ms (original), 5.5 ms (after improvement)

C. 6.0 ms (original), 5.7 ms (after improvement)

D. 6.2 ms (original), 5.9 ms (after improvement)

Correct Answer: A

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Question 24 View Details

A spreadsheet records monthly sales (units) of three products for a quarter. The data are:\n\n- Product A: Jan B2=120, Feb B3=150, Mar B4=130\n- Product B: Jan C2=80, Feb C3=95, Mar C4=100\n- Product C: Jan D2=200, Feb D3=210, Mar D4=190\n\nUnit prices are: A = \(\text{₦}500\), B = \(\text{₦}750\), C = \(\text{₦}300\). Commission is 5 % of the sales value for each product each month. In addition, if the total units sold in a month exceed 400, a bonus of \(\text{₦}20{,}000\) is added to that month's commission. Using appropriate spreadsheet formulas (you may describe them), calculate the total commission earned over the three months. State the final amount in naira.

A. ₦89,312.50

B. ₦33,312.50

C. ₦29,312.50

Correct D. ₦69,312.50

Correct Answer: D

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Question 25 View Details

A relational table STUDENT has attributes (StudentID, Name, Course, Year, Email). The functional dependencies are: \(StudentID \rightarrow Name, Course, Year, Email\); \(Email \rightarrow StudentID\); \(Course, Year \rightarrow StudentID\). Determine the highest normal form (1NF, 2NF, 3NF, BCNF) that the table satisfies, giving a brief justification.

A. 1NF

Correct B. BCNF

C. 2NF

D. 3NF

Correct Answer: B

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