5.4 Relationships, trends and confounders

NCA-GENM · Data Analysis and Visualization (10% of the exam) · Official objective: “Identify relationships and trends or any factors that could affect the results of research.”

Correlation versus cause, site-specific confounders and spotting trends.

Key points

  1. Correlation means two variables move together. It is not proof of cause. A hidden third factor, a confounder, can drive both.

    What NVIDIA says (2)

    “For any use case, be aware of the variables that are highly correlated, as they could skew results.”

    — Accelerated Data Analytics: Speed Up Data Exploration with RAPIDS cuDF

    “Take this into account if you are using any future algorithm that assumes the variables are independent, such as linear regression .”

    — Accelerated Data Analytics: Speed Up Data Exploration with RAPIDS cuDF

  2. A confounding factor affects both inputs and outcomes, making a false link look real. Single-site data can carry such site-specific bias.

    What NVIDIA says (1)

    “Medical institutions have had to rely on their own data sources, which can be biased by, for example, patient demographics, the instruments used or clinical specializations.”

    — What Is Federated Learning?

  3. Linking charts lets you slice data quickly and spot trends over time.

    What NVIDIA says (1)

    “a clear pattern emerges between weekday and weekend trips”

    — Accelerated Data Analytics: A Guide to Data Visualization with RAPIDS

Key terms

Sample question

A correlation matrix shows two features are strongly correlated. Why does that matter?

Show the answer

Answer: Highly correlated variables can skew results, especially for models that assume independence such as linear regression

Correlation means two variables move together. It is not proof of cause. A hidden third factor, a confounder, can drive both.

What NVIDIA says (2)

“For any use case, be aware of the variables that are highly correlated, as they could skew results.”

— Accelerated Data Analytics: Speed Up Data Exploration with RAPIDS cuDF

“Take this into account if you are using any future algorithm that assumes the variables are independent, such as linear regression .”

— Accelerated Data Analytics: Speed Up Data Exploration with RAPIDS cuDF

Practice 5.4 (3 questions) Full Data Analysis and Visualization guide

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