Data Value Conflicts and Redundancy in Data Integration

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What does 'incomplete' data refer to?

Data containing errors and outliers

Data with missing attribute values or lacking certain attributes (correct)

Data with intentional disguises

Data with discrepancies in codes or names

Which is an example of 'noisy' data?

Occupation=“ ” (missing data)

Was rating “1, 2, 3”, now rating “A, B, C”

Age=“42”, Birthday=“03/07/2010”

Salary=“−10” (an error) (correct)

In data cleaning, what is one reason for missing data?

Intentional disguises

Discrepancies in codes or names

Equipment malfunction (correct)

Duplicate records

How is missing data usually handled when the class label is missing?

Ignore the tuple Signup and view all the answers

What is a suggested method for filling in missing values automatically?

Use a global constant to fill in the missing value Signup and view all the answers

Why might certain data not be considered important at the time of entry?

Due to misunderstanding Signup and view all the answers

What does the null rule specify?

Handling blanks, question marks, special characters, or other indicative strings for null condition Signup and view all the answers

What is ETL in the context of data migration and integration?

Extraction/Transformation/Loading Signup and view all the answers

Which major task is NOT part of Data Preprocessing?

Data Visualization Signup and view all the answers

What is the purpose of data scrubbing in data cleaning?

Detecting errors using simple domain knowledge and making corrections Signup and view all the answers

What is the primary goal of data integration?

Combining data from multiple sources into a coherent store Signup and view all the answers

What does entity identification problem refer to in data integration?

Identifying real-world entities from multiple data sources Signup and view all the answers

What is a possible reason for attribute values from different sources to be different?

Different representations Signup and view all the answers

In data integration, what is one way to detect redundant attributes?

Correlation analysis Signup and view all the answers

What does a larger Χ2 value indicate in correlation analysis of nominal data?

Variables are more likely related Signup and view all the answers

In the Chi-Square calculation example provided, how is the Chi-Square value calculated?

Sum of squared differences between observed and expected counts Signup and view all the answers

What does the Correlation Coefficient measure in correlation analysis of numeric data?

The linear relationship between variables Signup and view all the answers

What does it mean when two attributes have a high Correlation Coefficient value?

They have a strong linear relationship Signup and view all the answers

What is the purpose of splitting in the context of unsupervised data preprocessing?

To recursively prepare data for further analysis like classification Signup and view all the answers

What is a common technique mentioned for data smoothing in the text?

Calculating bin means Signup and view all the answers

What is the purpose of concept hierarchy generation in a data warehouse?

To view data at multiple granularity levels Signup and view all the answers

How are concept hierarchies usually formed according to the text?

By recursively reducing data and replacing low level concepts with higher level ones Signup and view all the answers

Which task is NOT a part of data preprocessing based on the text?

Data partitioning into equal-frequency bins Signup and view all the answers

What does data transformation and discretization involve according to the text?

Replacing low level concepts with higher level ones Signup and view all the answers

What does a positive covariance between two variables indicate?

Both variables tend to be larger than their expected values Signup and view all the answers

What does a covariance of 0 between two variables suggest?

The variables are independent Signup and view all the answers

How does negative covariance impact the relationship between two variables?

If one variable is larger than its expected value, the other is likely smaller Signup and view all the answers

When does a covariance of 0 imply independence between two variables?

Only when the data follow multivariate normal distributions Signup and view all the answers

In the context of stock prices, what does it mean when two stocks have a positive covariance?

Their prices will rise together Signup and view all the answers

What is the relationship between correlation coefficient and covariance?

Correlation coefficient measures strength and direction, while covariance measures direction only Signup and view all the answers