Interview practice

Data Analyst

5–8 years · Senior — SQL · Excel · Power BI / Tableau · Statistics · Python · Stakeholder reporting

0–2 years 2–5 years 5–8 years 8+ years
technical Statistical analysis 1 of 6
You notice a significant p-value of 0.03 in a hypothesis test. What does this indicate regarding your null hypothesis, and what further steps do you take?
What a strong answer covers

Rejects the null hypothesis; checks the effect size to understand practical significance; considers the context and implications of the finding; evaluates assumptions of the test and checks for Type I and Type II errors; plans next steps for further validation or experiments.

The follow-up you would get

What do you do if the effect size is negligible despite a statistically significant p-value?

Could you have answered that?
technical Data visualisation 2 of 6
You've created a Power BI dashboard that stakeholders find confusing. What specific aspects do you evaluate to improve clarity and usability?
What a strong answer covers

Reviews user feedback and identifies pain points; assesses the choice of charts and whether they accurately represent the data; ensures consistent use of colours and labels; checks for unnecessary complexity or clutter; considers the flow of information and logical grouping of visuals.

The follow-up you would get

How do you determine which metrics are most important to display for stakeholder audiences?

Could you have answered that?
scenario Data Quality 3 of 6
You've been alerted that a data quality issue has been discovered after a report was sent to stakeholders, leading to incorrect insights. What do you do in the first half-hour?
What a strong answer covers

Identifies the extent of the issue and the data sources affected; checks the data ingestion process for anomalies; communicates with stakeholders about the potential impact; initiates a rollback to previous data state if necessary; documents findings for future reference.

The follow-up you would get

The issue stemmed from a recent ETL update. How do you ensure this does not occur again?

Could you have answered that?
scenario Stakeholder Reporting 4 of 6
You have a crucial presentation to stakeholders, but they request a last-minute change in metrics that requires extensive data manipulation. How do you manage this request?
What a strong answer covers

Assesses the feasibility of the request within the time constraints; prioritises the most impactful metrics to focus on; communicates risks and limitations to stakeholders; begins data extraction and manipulation in parallel to gathering feedback; prepares a backup plan in case of time constraints.

The follow-up you would get

The stakeholders are insistent on having the new metrics included. How do you negotiate the trade-offs?

Could you have answered that?
technical Data cleaning 5 of 6
You have a dataset with 100,000 rows where a key column has 5% missing values. What steps do you take to handle these missing values before analysis?
What a strong answer covers

Identifies the nature of the missing data (missing completely at random, missing at random, or missing not at random); considers using imputation methods such as mean, median, mode, or predictive model; checks for the impact on analysis and whether to exclude affected rows; assesses if it's appropriate to fill with a placeholder or create a new category.

The follow-up you would get

If you decide to impute values, how do you choose the method of imputation?

Could you have answered that?
ownership An incident you handled 6 of 6
Describe an incident where you had to manage a data-related crisis. What steps did you take?
What a strong answer covers

Details the context of the incident, including how it was discovered; outlines the immediate actions taken, such as data validation or stakeholder communication; explains how the resolution was achieved, including any tools or methods used; reflects on the long-term changes made to prevent recurrence; avoids blaming others for the situation.

The follow-up you would get

What indicators would you monitor earlier to catch similar incidents?

Could you have answered that?
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