Practice neco data_processing 2017 Past Questions

Question 1 View Details

A class of 30 students sat for a test. The total of all their scores is 2100 marks. The highest score obtained was 95 marks and the lowest was 45 marks. What is the average score of the remaining 28 students?

A. 80

B. 75

Correct C. 70

D. 65

Correct Answer: C

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Question 2 View Details

Consider a relation R(A,B,C,D) with the functional dependencies: A \rightarrow B, BC \rightarrow D, and D \rightarrow A. Determine (i) a candidate key for R, and (ii) the highest normal form (up to BCNF) that R satisfies.

Correct A. Candidate key: AC; Highest normal form: 1NF

B. Candidate key: AB; Highest normal form: 3NF

C. Candidate key: CD; Highest normal form: BCNF

D. Candidate key: AD; Highest normal form: 2NF

Correct Answer: A

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Question 3 View Details

A survey of 200 households shows that 40% own a car, 25% own a motorcycle and 15% own both a car and a motorcycle. How many households own a car but not a motorcycle?

A. 30

B. 80

C. 20

Correct D. 50

Correct Answer: D

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Question 4 View Details

The 8-bit two's complement binary number 11010110_2 is stored in a computer. What decimal integer does it represent?

A. -41

B. 214

Correct C. -42

D. -86

Correct Answer: C

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Question 5 View Details

Given the following tables: Employees(EmpID, DeptID, Salary): (1,10,5000), (2,10,7000), (3,20,6000), (4,20,8000), (5,30,5500) Departments(DeptID, ManagerID): (10,1), (20,3), (30,5) For each department, the manager is the employee whose EmpID equals ManagerID. Determine the DeptID(s) for which the average salary of all employees in that department is greater than the salary of its manager.

A. 30

B. 20, 30

C. 10, 30

Correct D. 10, 20

Correct Answer: D

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Question 6 View Details

In the data processing cycle the four steps are Input, Process, Output and Storage. The time taken for Input, Output and Storage are 5 s, 4 s and 6 s respectively. The total time for one complete cycle is 30 s. If the time taken for the Process step is reduced by 20%, the total cycle time is reduced by 3 s. Determine (i) the original time taken for the Process step (in seconds) and (ii) the new total cycle time (in seconds) after the reduction.

A. Original Process time = 16 s; New total cycle time = 28 s

B. Original Process time = 15 s; New total cycle time = 28 s

C. Original Process time = 14 s; New total cycle time = 26 s

Correct D. Original Process time = 15 s; New total cycle time = 27 s

Correct Answer: D

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Question 7 View Details

A Boolean function is defined as \(F = (A + \overline{B})(C + \overline{D})(\overline{E} + G)\). The function must be implemented using only NAND gates. What is the minimum number of NAND gates required for the implementation?

A. 15

B. 12

C. 14

Correct D. 13

Correct Answer: D

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Question 8 View Details

List the four main stages of the data processing cycle in their correct order.

A. Input, Output, Process, Storage

B. Process, Input, Output, Storage

Correct C. Input, Process, Output, Storage

D. Input, Process, Storage, Output

Correct Answer: C

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Question 9 View Details

A school keeps a student file containing the fields Admission No (unique), Name, Class and Scores. The following operations are frequently performed: (i) retrieve a student's full record when the Admission No is known, (ii) list all students in a given Class sorted alphabetically by Name, (iii) update a student's Scores. For each operation, recommend the most suitable type of file organization (Sequential, Indexed Sequential, Direct/Random) and briefly justify your choice.

A. (i) Indexed sequential file using Admission No as key; (ii) Sequential file sorted by Class then Name; (iii) Sequential file for updates

B. (i) Direct (random) access file using Name as key; (ii) Indexed sequential file organised by Scores then Name; (iii) Direct (random) access file using Class for updates

Correct C. (i) Direct (random) access file using Admission No as key; (ii) Indexed sequential file organised by Class then Name; (iii) Direct (random) access file for updates

D. (i) Sequential file using Admission No; (ii) Direct (random) access file organised by Class then Name; (iii) Indexed sequential file for updates

Correct Answer: C

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Question 10 View Details

Consider the relational schema STUDENT(AdmNo, Name, Class, Score) where AdmNo is unique for each student. Identify all candidate keys and state the primary key. Then write an SQL query that lists the names of students whose Score is above the average Score of their own Class.

A. Candidate key: (AdmNo, Class) (primary key). SQL: SELECT Name FROM STUDENT S WHERE Score > (SELECT AVG(Score) FROM STUDENT);

Correct B. Candidate key: AdmNo (primary key). SQL: SELECT Name FROM STUDENT S WHERE Score > (SELECT AVG(Score) FROM STUDENT WHERE Class = S.Class);

C. Candidate key: Name (primary key). SQL: SELECT Name FROM STUDENT S WHERE Score > (SELECT AVG(Score) FROM STUDENT WHERE Class = S.Class);

D. Candidate key: AdmNo (primary key). SQL: SELECT Name FROM STUDENT S WHERE Score >= (SELECT AVG(Score) FROM STUDENT WHERE Class = S.Class);

Correct Answer: B

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Question 11 View Details

Twenty students sat a mathematics test and obtained the following scores (in marks): 45, 52, 58, 60, 62, 65, 68, 70, 71, 73, 74, 76, 78, 80, 82, 85, 88, 90, 92, 95. (a) Calculate the arithmetic mean \( \bar{x} \) of the original scores. (b) Remove the two lowest and two highest scores and calculate the new mean \( \bar{x}_{\text{trim}} \) of the remaining data. (c) Based on the original data, state whether the distribution is positively skewed, negatively skewed, or symmetric.

A. Mean = 73.2; Trimmed mean = 73.75; Distribution is positively skewed

Correct B. Mean = 73.2; Trimmed mean = 73.75; Distribution is negatively skewed

C. Mean = 73.2; Trimmed mean = 72.5; Distribution is negatively skewed

D. Mean = 74.5; Trimmed mean = 73.75; Distribution is negatively skewed

Correct Answer: B

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Question 12 View Details

A computer stores the decimal number 156 in an 8‑bit unsigned binary format. (i) Write the 8‑bit binary representation. (ii) Convert that binary number to its equivalent hexadecimal representation.

A. 01100111, 67

Correct B. 10011100, 9C

C. 10011000, 98

D. 10011101, 9D

Correct Answer: B

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Question 13 View Details

A file of size 12,800 bytes is to be stored on a disk that uses blocks of 512 bytes. The file is allocated using linked allocation, where each block contains a 4‑byte pointer to the next block. (a) Determine the number of blocks required to store the file. (b) Calculate the total overhead in bytes due to the pointers. (c) State the overhead that would be incurred if the same file were stored using contiguous allocation (assume no overhead for contiguous allocation).

Correct A. 25 blocks, 100 bytes overhead, 0 bytes with contiguous allocation

B. 25 blocks, 0 bytes overhead, 0 bytes with contiguous allocation

C. 26 blocks, 104 bytes overhead, 0 bytes with contiguous allocation

D. 24 blocks, 96 bytes overhead, 0 bytes with contiguous allocation

Correct Answer: A

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Question 14 View Details

Consider the following sales data (in units) for three products over four quarters: Product A: Q1 1200, Q2 1500, Q3 1300, Q4 1700 Product B: Q1 800, Q2 950, Q3 1100, Q4 1050 Product C: Q1 1400, Q2 1600, Q3 1550, Q4 1700 (a) Compute the total annual sales for each product. (b) Find the overall average quarterly sales for the company (i.e., average of the total sales of each quarter). (c) Using a conditional sum, determine the total sales of Product B in those quarters where Product C's sales exceeded 1500 units. (d) For Product A, identify the quarter that experienced the greatest increase in sales compared with the preceding quarter.

A. A:5700, B:3900, C:6250; Avg quarterly = 3950; Conditional B total = 2950; Greatest increase for A in Q4

B. A:5700, B:3900, C:6250; Avg quarterly = 3962.5; Conditional B total = 3000; Greatest increase for A in Q2

Correct C. A:5700, B:3900, C:6250; Avg quarterly = 3962.5; Conditional B total = 3000; Greatest increase for A in Q4

D. A:5600, B:4000, C:6300; Avg quarterly = 4000; Conditional B total = 3100; Greatest increase for A in Q2

Correct Answer: C

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Question 15 View Details

A data processing system performs the following steps for each transaction, with the indicated processing times: Input - 2 s, Validation - 1 s, Processing - 3 s, Storage - 2 s, Output - 1 s, Feedback - 1 s. (a) Arrange these steps in the correct order of the data processing cycle. (b) Which step is primarily responsible for error checking? (c) What is the total time required to complete one full cycle?

A. Order: Input, Validation, Processing, Output, Storage, Feedback; Error checking in Processing; Total time = 9 s

B. Order: Input, Validation, Processing, Storage, Feedback, Output; Error checking in Storage; Total time = 10 s

Correct C. Order: Input, Validation, Processing, Storage, Output, Feedback; Error checking in Validation; Total time = 10 s

D. Order: Input, Processing, Validation, Storage, Output, Feedback; Error checking in Validation; Total time = 11 s

Correct Answer: C

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Question 16 View Details

During a data processing cycle, the four stages - Input (\(I\)), Process (\(P\)), Output (\(O\)) and Storage (\(S\)) - take the following relationships: the processing stage takes twice as long as the input stage, the output stage takes 5 minutes less than the input stage, and the storage stage occupies exactly \(30\%\) of the total cycle time. If the total time for one complete cycle is 55 minutes, determine the time (in minutes) taken by each stage and state what percentage of the total time is spent on processing.

A. Input = 11.0 min, Process = 22.0 min, Output = 6.0 min, Storage = 16.0 min; Processing accounts for 40.0 % of the total time.

Correct B. Input = 10.9 min, Process = 21.8 min, Output = 5.9 min, Storage = 16.5 min; Processing accounts for 39.5 % of the total time.

C. Input = 12.0 min, Process = 24.0 min, Output = 7.0 min, Storage = 12.0 min; Processing accounts for 43.6 % of the total time.

D. Input = 9.5 min, Process = 19.0 min, Output = 4.5 min, Storage = 22.0 min; Processing accounts for 34.5 % of the total time.

Correct Answer: B

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Question 17 View Details

An information system processes data in cycles consisting of three stages: Input (4 min), Process (6 min) and Output (3 min). After each output, the system checks the error level; if the error exceeds 2 % a feedback stage of 5 min is performed before the next input. The probability that the error exceeds the threshold for any given cycle is 0.25, independent of other cycles. If the system processes 8 independent batches, what is the expected total time (in minutes) required to complete all cycles?

A. 108 minutes

B. 112 minutes

Correct C. 114 minutes

D. 120 minutes

Correct Answer: C

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Question 18 View Details

A data processing centre can allocate at most 120 minutes of processing time per hour. For each record, the Input stage requires 2 min, the Process stage 5 min and the Output stage 1 min; storage time is negligible. (a) Assuming the stages are performed sequentially for each record, what is the maximum number of whole records that can be completely processed in one hour? (b) If the centre can pipeline the Input and Output stages so that they occur concurrently with the Process stage, what is the new maximum number of records that can be processed in one hour?

Correct A. (a) 7 records, (b) 12 records

B. (a) 9 records, (b) 15 records

C. (a) 8 records, (b) 13 records

D. (a) 6 records, (b) 10 records

Correct Answer: A

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Question 19 View Details

A. 260

B. 280

Correct C. 300

D. 310

Correct Answer: C

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Question 20 View Details

In relation \(R(A,B,C,D)\) the following functional dependencies hold: \(A \rightarrow B\), \(C \rightarrow D\), and \(AB \rightarrow C\).\n\n(a) List all candidate keys of \(R\).\n(b) State the highest normal form (up to BCNF) that \(R\) satisfies.\n(c) Decompose \(R\) into a collection of relations that are in BCNF.

A. (a) {A,B}; (b) 3NF; (c) R1(A,B) and R2(C,D)

B. (a) {C}; (b) 1NF; (c) R1(A,B) and R2(C,D)

C. (a) {A,C}; (b) BCNF; (c) R1(A,B,C) and R2(C,D)

Correct D. (a) {A}; (b) 2NF; (c) R1(C,D) and R2(A,B,C)

Correct Answer: D

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Question 21 View Details

A small business records its electricity meter reading at the start of the month as 12,350 kWh and at the end as 13,210 kWh. The tariff is tiered: the first \(500\) kWh are charged at ₦15 per kWh, the next \(300\) kWh at ₦20 per kWh, and any remaining consumption at ₦25 per kWh. A fixed service charge of ₦2,500 is added to the bill. The business also receives a government rebate of \(5\%\) on the total variable charge (the charge for consumption only, not the service charge). Determine the total amount payable for the month in naira.

Correct A. 16750

B. 17500

C. 17700

D. 16625

Correct Answer: A

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Question 22 View Details

Given the Boolean function \(F(A,B,C) = \Sigma m(1,2,5,6,7) + d(0,3)\), where \(d\) denotes don\'t‑care conditions, simplify \(F\) to a minimal sum‑of‑products expression using a Karnaugh map. Then state the minimum number of two‑input AND, OR, and NOT gates required to implement the simplified expression, assuming each gate counts as one.

Correct A. \overline{A} + A(B + C); 4

B. \overline{A} + AB + AC; 5

C. \overline{A} + A(BC); 3

D. A\overline{B} + C; 4

Correct Answer: A

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Question 23 View Details

A file of size \(10\,200\) bytes is to be stored on a disk that uses a block size of \(4\,\text{KB}\) (i.e., \(4\,096\) bytes). The file is stored using indexed allocation, where a single index block contains pointers to the data blocks. Determine (a) the number of data blocks required, (b) the total number of blocks (data plus index) actually occupied on the disk, and (c) the total amount of internal fragmentation in bytes. Compare these results with contiguous allocation for the same file.

A. Data blocks: 2; Total blocks: 3; Internal fragmentation: 1792 bytes; Contiguous uses 3 blocks (12,288 bytes) with same fragmentation.

Correct B. Data blocks: 3; Total blocks: 4; Internal fragmentation: 2088 bytes; Contiguous uses 3 blocks (12,288 bytes) with same fragmentation.

C. Data blocks: 3; Total blocks: 5; Internal fragmentation: 2088 bytes; Contiguous uses 4 blocks (16,384 bytes) with same fragmentation.

D. Data blocks: 4; Total blocks: 5; Internal fragmentation: 3072 bytes; Contiguous uses 3 blocks (12,288 bytes) with different fragmentation.

Correct Answer: B

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Question 24 View Details

Consider the relation \(R(A,B,C,D)\) with the set of functional dependencies \(A \rightarrow B,\; B \rightarrow C,\; C \rightarrow D\). (a) List all candidate keys of \(R\). (b) State the highest normal form (up to BCNF) that \(R\) satisfies. (c) Decompose \(R\) into a collection of relations that are in Boyce‑Codd Normal Form (BCNF).

A. Candidate key: D; Highest NF: 2NF; BCNF decomposition: R1(A,D) and R2(B,C)

B. Candidate key: B; Highest NF: 1NF; BCNF decomposition: R1(A,B) and R2(C,D)

Correct C. Candidate key: A; Highest NF: 2NF; BCNF decomposition: R1(B,C) and R2(A,B,D)

D. Candidate key: A; Highest NF: 3NF; BCNF decomposition: R1(A,B) and R2(B,C,D)

Correct Answer: C

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Question 25 View Details

A company enforces a password policy requiring passwords to be at least eight characters long and to contain at least one uppercase letter, one lowercase letter, one digit, and one special character. An employee creates the password "Pass2023!". The company stores passwords as unsalted MD5 hashes. A data breach exposes the list of password hashes. Assume an attacker possesses pre‑computed rainbow tables covering \(10^{7}\) common passwords, none of which match "Pass2023!". The attacker can compute \(10^{9}\) hash evaluations per second and estimates that the total number of possible passwords satisfying the policy is \(2^{48}\). (a) Estimate the expected time, in days, for the attacker to recover the password by brute‑force (assuming the average case of trying half the key space). (b) Briefly discuss two ethical or security implications of the company's password storage practice.

A. Approximately 0.8 days; storing unsalted MD5 hashes is safe because they cannot be reversed, ensuring confidentiality.

B. Approximately 3.2 days; using unsalted MD5 hashes provides strong integrity but may expose password length, compromising privacy.

Correct C. Approximately 1.6 days; storing unsalted MD5 hashes is insecure and allows easy identification of reused passwords, violating confidentiality and privacy.

D. Approximately 0.5 days; unsalted MD5 hashes are acceptable as they prevent attackers from learning the original passwords, maintaining security.

Correct Answer: C

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