Practice neco data_processing 2021 Past Questions

Question 1 View Details

Relation R(A,B,C,D) has functional dependencies: \(A \rightarrow B\), \(BC \rightarrow D\), \(D \rightarrow A\). Determine the number of candidate keys of R. Then, if R is decomposed into R1(A,B) and R2(B,C,D), state whether the decomposition is lossless‑join.

A. 3 candidate keys; the decomposition is not lossless‑join.

B. 1 candidate key; the decomposition is not lossless‑join.

Correct C. 2 candidate keys; the decomposition is not lossless‑join.

D. 2 candidate keys; the decomposition is lossless‑join.

Correct Answer: C

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Question 2 View Details

Given a 3‑variable Boolean function \(F(A,B,C)\) defined by the minterms \(m(1,3,4,6)\) and don't‑care conditions \(d(0,7)\), find a minimal sum‑of‑products expression for \(F\) and state the total number of literals in that expression.

A. F = \overline{A}\,\overline{B} + \overline{A}\,C + B C; total literals = 7.

B. F = \overline{A}\,B + \overline{B}\,\overline{C} + A C; total literals = 6.

Correct C. F = \overline{A}\,\overline{B} + \overline{B}\,\overline{C} + B C; total literals = 6.

D. F = \overline{A}\,\overline{C} + \overline{B}\,C + A B; total literals = 6.

Correct Answer: C

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Question 3 View Details

In a data processing system the stages are Input, Processing, Output, Storage and Control. An error is discovered in the final output report that was caused by incorrect data entered during the Input stage. At which stage should the correction be made to prevent the error from recurring, and what action should be taken?

A. Correction at the Processing stage by adjusting the algorithm (modify code) and then re‑run the data.

B. Correction at the Output stage by editing the final report (re‑format or re‑type) without changing source data.

C. Correction at the Storage stage by updating the database entries (re‑store or edit records) and then re‑process the data.

Correct D. Correction at the Input stage by fixing the source data (re‑enter or edit the records) and then re‑process the data.

Correct Answer: D

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Question 4 View Details

A batch processing system handles 10,000 records. During the Validation stage 5 % of the records are found to be invalid and are discarded. The Processing stage requires 2 minutes for every 100 valid records. Calculate the total processing time required for the valid records, and express the answer in hours and minutes.

A. 3 hours 30 minutes (210 minutes).

B. 2 hours 50 minutes (170 minutes).

Correct C. 3 hours 10 minutes (190 minutes).

D. 4 hours 0 minutes (240 minutes).

Correct Answer: C

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Question 5 View Details

Given the Boolean function \(F = (A + \overline{B})\cdot (\overline{A} + C)\), determine the minimum number of 2‑input NAND gates required to implement \(F\) using only NAND gates. Show the conversion steps.

A. 8 NAND gates

B. 5 NAND gates

Correct C. 6 NAND gates

D. 7 NAND gates

Correct Answer: C

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Question 6 View Details

Consider the Boolean function \(F(A,B,C,D) = (A + \overline{B})(C + \overline{D}) + \overline{A} B \overline{C}\). Determine how many distinct input combinations (minterms) produce an output of 1 for \(F\). Show your reasoning.

A. 12

B. 8

C. 4

Correct D. 16

Correct Answer: D

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Question 7 View Details

A relation R(A,B,C,D,E) has the functional dependencies: A \rightarrow B, A \rightarrow C, BC \rightarrow D, D \rightarrow E.\n\n(a) List all candidate keys of R.\n(b) State the highest normal form that R satisfies.\n(c) If R is not in BCNF, decompose it into BCNF relations and list the resulting schemas.

A. Candidate key: {A}. Highest normal form: 3NF. BCNF decomposition: R1(A,B), R2(C,D,E), R3(D,E).

B. Candidate key: {A,B}. Highest normal form: 1NF. BCNF decomposition: R1(A,B), R2(C,D,E).

C. Candidate key: {BC}. Highest normal form: 3NF. BCNF decomposition: R1(B,C), R2(A,D,E).

Correct D. Candidate key: {A}. Highest normal form: 2NF. BCNF decomposition: R1(B,C,D), R2(A,B,C,E), R3(D,E).

Correct Answer: D

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Question 8 View Details

The following monthly sales (in units) are recorded for three products over six months:\n\n| Month | Product X | Product Y | Product Z |\n|-------|-----------|-----------|-----------|\n| Jan | 120 | 100 | 90 |\n| Feb | 150 | 110 | 95 |\n| Mar | 130 | 115 | 85 |\n| Apr | 160 | 105 | 100 |\n| May | 140 | 120 | 110 |\n| Jun | 155 | 130 | 105 |\n\n(a) Write a single array formula that returns, for each product, the total sales for the months in which that product's sales exceed the overall average monthly sales across all products.\n(b) Using the totals obtained, identify which product has the highest such total and by how much it exceeds the next highest total.\n(c) Recommend an appropriate chart type to display these three totals and justify your choice.

A. Overall average ≈ 119.00 units. Totals: X = 820, Y = 260, Z = 10. Product X has the highest total, exceeding Product Y by 560 units. A line chart is appropriate because it shows trends over time.

B. Overall average ≈ 120.00 units. Totals: X = 800, Y = 300, Z = 20. Product Y has the highest total, exceeding Product X by 100 units. A stacked bar chart is appropriate because it highlights each product's contribution to the total.

C. Overall average ≈ 115.50 units. Totals: X = 870, Y = 240, Z = 5. Product X has the highest total, exceeding Product Z by 865 units. A pie chart is appropriate because it displays the proportion of each product's total.

Correct D. Overall average ≈ 117.78 units. Totals: X = 855, Y = 250, Z = 0. Product X has the highest total, exceeding Product Y by 605 units. A clustered column chart is appropriate because it compares the three totals clearly.

Correct Answer: D

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Question 9 View Details

A computer operates with a clock speed of 2 GHz. Each instruction requires 1 fetch cycle, 2 decode cycles, 1 execute cycle and 1 store cycle (total 5 cycles per instruction). A program consists of 1.2 million instructions.\n\n(a) Calculate the total execution time of the program.\n(b) Which stage of the instruction cycle is the bottleneck, and why?

A. Total execution time = 2.5 ms. The fetch stage is the bottleneck because it occurs first in each instruction.

B. Total execution time = 3 ms. The store stage is the bottleneck because it uses 1 of the 5 cycles per instruction, the greatest share.

Correct C. Total execution time = 3 ms. The decode stage is the bottleneck because it uses 2 of the 5 cycles per instruction, the greatest share.

D. Total execution time = 4 ms. The execute stage is the bottleneck because it requires the most complex operations.

Correct Answer: C

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Question 10 View Details

The test scores of ten students are: 68, 75, ?, 82, 90, 55, ?, 77, 84, 69. The symbol ? denotes a missing score. Replace each missing value with the average of the known scores, then compute the new overall average. Finally, determine the percentage of students whose (imputed) scores are above 70.

Correct A. Average = 75; 70 % of students scored above 70.

B. Average = 73; 60 % of students scored above 70.

C. Average = 75; 60 % of students scored above 70.

D. Average = 77; 80 % of students scored above 70.

Correct Answer: A

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Question 11 View Details

Consider a relation R(A,B,C,D,E) with functional dependencies \(A \rightarrow B\), \(BC \rightarrow D\), \(D \rightarrow E\), and \(AB \rightarrow C\). (a) List all candidate keys of R. (b) Decompose R into BCNF and give the resulting relation schemas.

A. Candidate key: {AB}. BCNF decomposition: R1(B,C,D), R2(A,B), R3(A,E), R4(C,E).

B. Candidate key: {A,D}. BCNF decomposition: R1(A,B), R2(B,C), R3(C,D), R4(A,E).

Correct C. Candidate key: {A}. BCNF decomposition: R1(B,C,D), R2(A,B), R3(A,C), R4(A,E).

D. Candidate key: {B}. BCNF decomposition: R1(A,B,C), R2(B,D), R3(D,E), R4(A,E).

Correct Answer: C

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Question 12 View Details

A file contains 10,000 records each 100 bytes. The disk block size is 4\,KB. An indexed‑sequential file uses a primary index that fits in one block. Disk seek time = 5\,ms, rotational latency = 4\,ms, and transfer time = 0.02\,ms per KB. Assuming records are uniformly distributed, calculate the average time (in milliseconds) required to locate a record.

A. 20.4 ms (approximately)

B. 22.1 ms (approximately)

Correct C. 18.2 ms (approximately)

D. 15.6 ms (approximately)

Correct Answer: C

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Question 13 View Details

State the four stages of the data‑processing cycle in their correct order.

A. Input, Processing, Storage, Output

B. Processing, Input, Output, Storage

Correct C. Input, Processing, Output, Storage

D. Input, Output, Processing, Storage

Correct Answer: C

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Question 14 View Details

Classify each of the following as qualitative or quantitative data: (i) colour of a car, (ii) temperature in Celsius, (iii) number of students in a class.

A. (i) Quantitative, (ii) Qualitative, (iii) Quantitative

Correct B. (i) Qualitative, (ii) Quantitative, (iii) Quantitative

C. (i) Qualitative, (ii) Quantitative, (iii) Qualitative

D. (i) Qualitative, (ii) Qualitative, (iii) Quantitative

Correct Answer: B

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Question 15 View Details

The Boolean function \(F(A,B,C,D)\) is defined by the minterms \(\Sigma m(1,3,4,6,9,11,12,14)\). (a) Simplify \(F\) using a Karnaugh map and give the minimal sum‑of‑products expression. (b) If each NOT gate is a separate gate, each 2‑input AND gate counts as one gate and each 3‑input OR gate counts as one gate, determine the total number of gates required to implement the minimal expression.

Correct A. Minimal SOP: F = \overline{B}D + B\overline{D}; total gates required = 5

B. Minimal SOP: F = \overline{B}\overline{D} + BD; total gates required = 5

C. Minimal SOP: F = \overline{B}D + B\overline{D}; total gates required = 6

D. Minimal SOP: F = \overline{A}C + AD; total gates required = 5

Correct Answer: A

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Question 16 View Details

A data file contains the two consecutive 8‑bit binary patterns \(01000001_2\) and \(01100001_2\). Determine the decimal value of each byte and state the corresponding ASCII characters.

A. 66 (B) and 98 (b)

B. 66 (B) and 97 (a)

C. 65 (A) and 98 (b)

Correct D. 65 (A) and 97 (a)

Correct Answer: D

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Question 17 View Details

A plain‑text document contains 2,500 characters. Each character occupies 1 byte. The file format adds a 128‑byte header. What is the total file size in kilobytes (KB), rounded to two decimal places?

A. 2.63 KB

Correct B. 2.57 KB

C. 2.56 KB

D. 2.44 KB

Correct Answer: B

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Question 18 View Details

A small business records daily sales data for a week. Each day has 120 transactions, and each transaction is recorded with 5 fields, each field requiring 8 bytes of storage. After processing, a summary report stores only the total sales for each day as an 8‑byte number. If the raw data for the whole week is retained and the summary report is stored separately, calculate the ratio of the storage required for the raw data to that required for the summary report.

A. 480

Correct B. 600

C. 4200

D. 560

Correct Answer: B

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Question 19 View Details

A photographer captures images at a resolution of \(4000 \times 3000\) pixels with 24‑bit colour depth. Each image can be stored uncompressed or compressed using JPEG, which reduces the file size by 85 % on average. She has a 16 GB USB drive for storage and wishes to keep a compressed backup of each image on a cloud service that charges ₦0.02 per megabyte per month. Determine (a) the maximum number of images she can store on the USB drive, and (b) the total cost of cloud storage for those images over a period of 6 months.

Correct A. 2,962 images; ₦1,919.38

B. 522 images; ₦1,916.78

C. 2,962 images; ₦1,599.48

D. 444 images; ₦1,918.08

Correct Answer: A

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Question 20 View Details

A survey of 200 students recorded the number of hours they spend on ICT each week. The data were grouped as follows: 0-4 hrs: 30 students; 5-9 hrs: 50 students; 10-14 hrs: 70 students; 15-19 hrs: 40 students; 20-24 hrs: 10 students. Assuming the midpoint of each class represents all students in that class, (a) calculate the estimated mean number of hours per week, and (b) if the school wants to raise the average by 10 % by adding 5 extra hours per week to each student in the 0-4 hr group, how many additional total hours must be added across all students to reach the target mean?

Correct A. 65

B. 55

C. 80

D. 70

Correct Answer: A

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Question 21 View Details

Company X is evaluating three independent security controls. The firewall prevents a breach with probability \(0.6\) and costs \(\text{₦}200{,}000\). The antivirus prevents a breach with probability \(0.4\) and costs \(\text{₦}120{,}000\). Employee training prevents a breach with probability \(0.5\) and costs \(\text{₦}150{,}000\). Assuming the controls operate independently, the overall breach probability when a set of controls is implemented equals the product of the individual failure probabilities \((1-p)\). Management requires the overall breach probability to be at most \(0.20\). Determine the combination of controls that meets this requirement at the minimum total cost, and state that minimum cost in naira.

Correct A. 350000

B. 320000

C. 270000

D. 470000

Correct Answer: A

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Question 22 View Details

A data set consists of the five numbers \(12, 15, 9, 20, 14\). Find the median of this data set.

A. 12

B. 15

C. 13

Correct D. 14

Correct Answer: D

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Question 23 View Details

In a spreadsheet, column A lists the number of units sold, column B the unit price (in naira), and column C the total revenue for each row. The data are as follows:\n\nRow 1: A=40, B=150, C=6000\nRow 2: A=25, B=200, C=5000\nRow 3: A=30, B=180, C=5400\nRow 4: A=22, B=250, C=5600\nRow 5: A=35, B=160, C=5600\n\nIdentify the row that contains an incorrect total revenue, give the correct revenue for that row, and state the corrected grand total of column C after fixing the error.

A. Row 4; 5500; 27400

B. Row 5; 5600; 27500

C. Row 4; 5600; 27600

Correct D. Row 4; 5500; 27500

Correct Answer: D

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Question 24 View Details

A company follows the data‑processing cycle consisting of four phases: Input, Processing, Output and Storage. The following tasks and their durations are recorded:\n\n- Data collection: 3 days\n- Data validation: 2 days\n- Data storage: 1 day\n- Data analysis: 4 days\n- Data presentation: 2 days\n\nAssign each task to the appropriate phase, then calculate the percentage of the total cycle time spent in each phase. Express each percentage to one decimal place.

A. Input 25.0%, Processing 49.9%, Output 16.7%, Storage 8.4%

B. Input 20.0%, Processing 45.0%, Output 25.0%, Storage 10.0%

C. Input 16.7%, Processing 25.0%, Output 50.0%, Storage 8.3%

Correct D. Input 25.0%, Processing 50.0%, Output 16.7%, Storage 8.3%

Correct Answer: D

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Question 25 View Details

A small business is comparing two data‑backup options.\n\nOption A: a cloud backup service costing \(\text{₦}30{,}000\) per year, with no upfront fee.\nOption B: purchase an external server for \(\text{₦}100{,}000\) upfront and pay an annual maintenance fee of \(\text{₦}5{,}000\).\n\nThe business values a successful backup at \(\text{₦}30{,}000\) each year (i.e., the benefit of avoiding data loss). Determine after how many whole years the cumulative net benefit (benefit minus all costs) of Option B exceeds that of Option A.

Correct A. 5

B. 6

C. 4

D. 7

Correct Answer: A

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