Eight people, 32 more minutes of sleep. Real, or luck?
The paired t-test is the sharpest tool in the drawer because it compares each subject to themselves: natural short sleepers and long sleepers stop being noise, and only the change counts.
Health Starter Statistics free
After you install, this is the model to open.
Does Cutting Caffeine Buy You Sleep?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
The answer
All eight slept more, and the statistics agree that pattern is no fluke:
- t statistic
- -9.51
- p (two-tail)
- 0.00003
- Improved
- 8 of 8 people
A difference this consistent arises by chance about three times in a hundred thousand. That is the power of pairing: eight subjects settle what an unpaired design would need dozens for. Use it for anything measured twice on the same units: page speed before and after a fix, plants before and after fertiliser, reps before and after training.
The model
Eight people logged average nightly sleep, cut afternoon caffeine for two weeks, and logged again. Two columns, one row per person; the test works entirely on each row's difference.
| Before | mean 6.03 h |
| After | mean 6.56 h |
| Gain | about 32 min/night |
| t and p-value | calculated |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
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