Guide · 6 min read

How to Write a Data Analysis Report

A data analysis report translates numbers into a decision. Markers want the right method, but they reward a clear question, honest cleaning, readable charts and recommendations that follow from the evidence.

Start with the question and the reader

Every analysis begins with a business question, and every report ends with an answer. Before you open the data, write one sentence for each of these: what decision will this support, who will read the report and what would change their mind. A report that opens with here is the data I have rarely ends well. A report that opens with can we cut delivery cost without losing customers? tells you what to look for and what to ignore.

Write for a manager who is intelligent but not a statistician. Methods belong in the report, but the headline findings should be readable without them.

A standard structure

SectionWhat it containsShare of the report
Title and executive summaryThe question, the main findings with numbers and the recommendation, on one page5 to 10 percent
Background and objectivesBusiness context, the decision at stake and the specific questions5 to 10 percent
DataSource, period, variables, sample size and how the data were cleaned10 to 15 percent
MethodThe techniques used and why they fit the question5 to 10 percent
ResultsTables and charts with short interpretation, one finding per section30 to 40 percent
Discussion and limitationsWhat the results mean, what could be wrong, what was not tested10 to 15 percent
RecommendationsSpecific actions linked to findings5 to 10 percent
AppendicesFull output, code or formulas, data dictionaryNot counted

See our guide to executive summaries and business report format for the front and layout.

Describe and clean the data honestly

Readers need to know what you analyzed. Describe where the data came from, the time period, how many records you started with and how many you used. Then explain what you changed.

IssueWhat to doWhat to report
Missing valuesDecide whether to remove, fill with a sensible value or analyze separatelyHow many were missing, and which method you chose and why
DuplicatesRemove exact duplicatesHow many were removed
OutliersCheck whether they are errors or genuine extremes before removing themWhich values, and the reason you kept or removed them
Inconsistent formatsStandardize dates, units, spellings and categoriesThe rules applied
Impossible valuesSuch as negative quantities or future dates; investigate and correct or removeThe count and treatment

A short sentence such as of 5,214 order records, 112 duplicates and 38 records with missing delivery dates were removed, leaving 5,064 for analysis, builds trust. Never silently drop data. Keep a data dictionary in the appendix describing each variable, its unit and its meaning.

Match the method to the question

If the question is...Typical methodReported as
What does the data look like?Descriptive statistics and chartsMeans, medians, spreads, distribution plots
Is there a difference between groups?Hypothesis testsTest statistic, p-value and effect size
Are two things related?Correlation or cross-tabulationCorrelation coefficient or chi-square result
What drives an outcome?RegressionCoefficients, R-squared and significance
What will happen next?ForecastingForecast values and accuracy measures
How can we group customers?Segmentation or clusteringSegment profiles and sizes

State why you chose the method, and state its main assumptions. See our guides on hypothesis testing and regression.

Choose charts that answer the question

You want to showBest chartAvoid
Change over timeLine chartPie charts or 3D bars
Comparison across categoriesBar chart, sorted by sizeToo many categories on one pie
Share of a whole (few parts)Stacked bar or a simple pie with three to five slicesPies with many slices
Distribution of one variableHistogram or box plotBar charts with arbitrary bins
Relationship between two variablesScatter plot, with a trend line if usefulLines connecting unrelated points
Exact valuesA tableA chart with unreadable labels
  • One message per chart Write the message as the title, such as Online orders grew 18 percent while store sales fell 4 percent.
  • Label everything Axes, units, legend and source.
  • Start bar axes at zero Truncated axes exaggerate differences.
  • Cut decoration Remove gridlines, shadows and 3D effects that do not help.
  • Refer to every chart in the text Say what to notice before the chart appears.

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Translate statistics into plain English

Statistical statementBusiness wording
The difference is significant at the 5 percent level (p = 0.026)It is unlikely that the difference is just luck, and we can reasonably act on it
The slope coefficient is 4.11 (p < .001)Each extra $1,000 of advertising was associated with about $4,100 more in sales
R-squared is 0.62The model explains about 62 percent of the variation in sales; the rest comes from other factors
The confidence interval is $0.40 to $6.00The true improvement is likely to be somewhere between 40 cents and six dollars per customer
We fail to reject the null hypothesisThe data do not give strong evidence of a difference

Always add what it means for the decision. The number is not the finding. The finding is what the number says about the question.

A worked results paragraph

Results write-up (hypothetical)

Finding 1: The new layout increases spending. Customers in stores with the new layout spent an average of $48.20 (n = 40), compared with $45.00 in stores with the old layout (n = 45). A two-sample t-test indicates the difference of $3.20 is statistically significant (t = 2.27, p = .026). A 95 percent confidence interval suggests the true increase lies between about $0.40 and $6.00 per visit. The effect is modest but, at current traffic, would be worth roughly $70,000 a year across the chain.

Limitation: stores were not randomly assigned, so differences in location or customer mix could account for part of the effect.

Recommendation: extend the new layout to ten more stores selected at random, and repeat the test before a chain-wide rollout.

The figures are invented. Notice that the paragraph leads with the finding, supports it with the statistic, quantifies the likely range, says what it is worth, notes a limitation and ends with an action.

A model findings paragraph

Reporting a result in plain language (hypothetical)

Customers who used the mobile app spent more per order than those who did not: $64 against $52 on average, a difference of $12 (23 percent). The difference is unlikely to be chance (p < .01), but app users also order more often and skew toward higher-income postal codes, so the app alone may not explain it. A test that matches users with similar non-users is the next step.

The paragraph gives the result, the size, the evidence, the caveat and the next step in four sentences.

Stating assumptions and limits

  • Data source and period Where the data came from and what dates they cover.
  • Cleaning decisions What you removed or fixed and why.
  • Missing data How much and how it was handled.
  • Method choice Why this test or model suits the question.
  • What the data cannot show Causation, other groups, other periods.

Limitations, recommendations and the appendix

Showing the limits of your analysis builds credibility. Typical limitations include a small or unrepresentative sample, a short time period, missing variables, data quality problems and the fact that observational data cannot prove causation. Say which apply and how they could affect the result. Do not hide behind them, though. After describing limits, say what you would do about each, such as collecting more data.

Recommendations should follow from findings, be specific and say who should do what. Put detailed output, code or spreadsheet formulas in an appendix so a reader can check your work. Our guides on Excel formulas and pivot tables and dashboards help with the analysis behind the report.

  • A clear question and a clear answer The first page should tell the reader both.
  • Honest data description Sources, size, cleaning steps and a data dictionary.
  • A method that fits State why, and state its assumptions.
  • Readable charts One message each, labeled, and referred to in the text.
  • Plain-English interpretation Say what the numbers mean for the decision.
  • Limits and next steps Say what could be wrong and what to do about it.

If you want help with the analysis or the report, you can order a data analysis report and upload your data and brief.

Quick answers

How much code or output should go in the report?

Keep the main body readable. Include key tables and charts in the text, and put full software output, code or formulas in an appendix.

Do I need to explain the statistical method?

Yes, briefly. Say what you used, why it fits the question and what assumptions you checked, without turning the report into a textbook.

How should I handle outliers?

Investigate first. If an outlier is an error, correct or remove it and say so. If it is genuine, consider reporting results with and without it.

What if my results are not significant?

Report that honestly. A null result is a valid finding. Discuss sample size, effect size and what the confidence interval shows.

How technical should the report be?

Match the reader. Put plain-language findings first and methods and detail in an appendix.

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