Data Summary in Excel: Reading Your Data with Descriptive Statistics & AI

Before you can analyze anything, you have to understand what your data looks like. This tutorial shows how to summarize a large table into a handful of key numbers, using Microsoft Copilot inside Excel (and ChatGPT outside it) for an instant overview and the core statistics functions to verify the details yourself.

Table of Contents

• What a Data Summary Is
• Let Copilot & ChatGPT Summarize for You
• The Statistics Behind the Summary
• AVERAGE: the typical value
• MEDIAN: the middle value
• MODE.SNGL: the most common value
• MIN and MAX: the spread
• COUNT and COUNTA: how many values
• STDEV.P and VAR.P: how spread out
• Best Practices

What a Data Summary Is

A data summary condenses a whole column of numbers into a few statistics that describe it at a glance. Instead of reading 500 rows, you look at five numbers and immediately know the typical value, the range, and how consistent the data is.

Every analysis in this series starts with a summary. You need a clear picture of the data before you hunt for trends, outliers, or correlations.

Throughout these tutorials we use the same small sales table, named Sales, in cells A1:G16:

Let Copilot & ChatGPT Summarize for You

Two AI helpers do the heavy lifting in this series, and it helps to know which to reach for:

• Microsoft Copilot (built into Excel, Microsoft 365) — works inside your workbook. Give it a plain-English instruction and it builds summaries, charts, and PivotTables in place.
• ChatGPT (web or app, used outside Excel) — paste a column of data or a result and ask it to explain, check, or write the formula for you. Great when you're stuck before you even open a formula.

With Copilot in Excel

Click any cell in your table, open the Copilot pane, and type a question in plain English.

Example prompt:

Summarize the Sales column. What are the average, the highest and the lowest sale?

Copilot returns the average, maximum, and minimum instantly, and often suggests a chart on its own. It's the fastest way to get a first read on any data.

With ChatGPT (outside Excel)

Copy the Sales column (or just the numbers) into ChatGPT and ask it directly:

Here are 15 sale amounts: 1200, 600, 1200, ... (paste all 15)
Give me the average, median, min, max, and standard deviation, and tell me in plain words what they mean.

ChatGPT replies with the numbers and a plain-language reading of them — handy when you want the "so what" explained before building anything in Excel. You can also ask it to write the formula first: "Give me the Excel formula for the median of cells G2 to G16" — then paste that into Excel.

Tip: Use Copilot when you want the result inside the workbook; use ChatGPT when you want help understanding or drafting before you build. Both appear throughout this series.

The Statistics Behind the Summary

AI gives you the answer fast, but the functions below let you build the same numbers yourself. They stay where you put them, update when the data changes, and plug straight into reports. Each one is the manual version of part of an AI summary.

AVERAGE: the typical value

The average (arithmetic mean) is the sum of all values divided by how many there are. It's the most common answer to "what's normal here?".

Syntax: =AVERAGE(number1, [number2], ...)

=AVERAGE(G2:G16)

This adds up all 15 sales in column G and divides by 15. The result is a typical sale amount for the period.

MEDIAN: the middle value

The median is the value exactly in the middle once everything is sorted. It's more honest than the average when a few huge or tiny values skew the picture.

=MEDIAN(G2:G16)

If one customer places a $10,000 order, the average jumps even though most orders are small, but the median barely moves. Use it whenever your data has extreme values.

MODE.SNGL: the most common value

The mode is the value that appears most often.

=MODE.SNGL(G2:G16)

This returns the sale amount that appears most often — $1,200, because six orders were exactly that. It answers "most popular" rather than "typical".

MIN and MAX: the spread

MIN and MAX give the smallest and largest values, defining the full range of the data.

=MIN(G2:G16)
=MAX(G2:G16)

The gap between the two tells you how wide the range is. A $250 minimum and a $2,400 maximum show the business serves both small and large orders.

COUNT and COUNTA: how many values

COUNT counts cells that contain numbers; COUNTA counts every non-empty cell.

=COUNT(G2:G16)
=COUNTA(B2:B16)

COUNT(G2:G16) returns the number of numeric sales. COUNTA(B2:B16) counts every date, which is handy for spotting blank rows. Comparing the two reveals missing values.

STDEV.P and VAR.P: how spread out

Standard deviation measures the average distance of values from the mean. Variance (VAR.P) is its square. A small standard deviation means values hug the average; a large one means they're scattered.

=STDEV.P(G2:G16)
=VAR.P(G2:G16)

Use STDEV.P when the table holds the entire population of data. If it's just a sample of a bigger population, use STDEV.S instead — more on that in Common Mistakes.

Best Practices

• Turn your range into a named table (Ctrl+T) so formulas like Sales[Sales] stay readable and update automatically.
• Let Copilot do the first pass inside Excel, then verify the key numbers with formulas before reporting them. If Copilot isn't available, paste the column into ChatGPT and ask it to sanity-check the average and range.
• Run a quick data-quality check first: ask Copilot (or ChatGPT) to count blanks and errors in the table.