Working With Data in Excel

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Working With Data in Excel

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Three sessions of numbers, none of them yours

The risk difference, the hypertensive counts, the percentages: all printed, none typed. A mentorship plan that cannot insert a lab here is a syllabus, not a room.

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What this session is not

It is not an Excel course. It is not a new paper. It is the earlier numbers, made rather than received, so the next session can talk about means and medians with a student who has already produced both.

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Act I · A Sheet Is a Dataset, Not a Report

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One row per person, one column per variable

Session 2’s rectangle becomes a sheet. If that rule is broken, every later formula is decorating a mess.

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The header row is one row, and it is the top one

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Codes, not labels

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A blank is not a zero, and 999 is a disaster

Missingness is a decision that has to stay visible. Filling it with zero invents patients. Coding it as 999 invents giants. Both destroy a mean before anyone has chosen a test.

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Five ways the same twenty patients were entered wrongly

The practice register is simulated and says so on the frame. The mistakes are not. They are the ones that quietly sit under a finished Table 1.

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Khanam’s Table 1 is a report, not a dataset

A table is the answer to questions already asked. A dataset is what you ask the next question of. Confusing the two is how people try to ‘analyze’ a published table and think they have the study.

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Act II · Addresses, Formulas, and the Denominator That Moved

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Every cell has an address

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A formula starts with an equals sign

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A range is two addresses and a colon

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Drag it down and the addresses move with it

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The dollar sign holds one part of an address still

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Session 3’s error, now visible on screen

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Act III · Counting a Categorical Column

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COUNT counts numbers; COUNTA counts anything

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COUNTIF asks a question of a column

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A percentage is a count over a denominator you chose

Session 3’s sentence becomes a formula. The denominator is still a choice. Excel will not make it for you; it will only remember the choice you typed.

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COUNTIFS makes a two-way table

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Row or column percentage: one reference apart

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The same table without typing a formula

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100.1 is not always an error

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Act IV · Summarizing a Numerical Column

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Four functions, one column

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Quartiles and percentiles

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The five-number summary, as one block

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77.0 centimetres, and where you have seen it

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When the mean and the median part company

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STDEV.S or STDEV.P

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The card to keep beside the keyboard

A short list, not a software syllabus. COUNT, COUNTIF, the five-number summary, and the one rule about missing values. Session 4 then asks which of those numbers a paper should print.

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What the next session does with all of this