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Update DST SWITRS with t-test

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agude committed Oct 14, 2018
1 parent d3b95fe commit 2661f23d005a97206a03eca02f1078de9ae0fec4
@@ -71,7 +71,30 @@ stays high the entire week. This indicates that it takes even longer than a
week for people to catch up on sleep and for the accident rate to go back to
normal.

Daylight savings time causes more accidents, but those of us in California
## _t_-Test

So the "_chi-by-eye_" plot is suggestive, but I can quantify whether the
results are significant using a [two-tailed paired _t_-test][paired_t-test].
This is the method Varughese & Allen use. Doing so gives the following
results.

[paired_t-test]: https://en.wikipedia.org/wiki/Student%27s_t-test#Paired_samples

| Day | _t_-value | _p_-value |
|:-------------|----------:|------------:|
| **Monday** | 2.7 | **0.017** |
| **Tuesday** | 2.5 | **0.023** |
| Wednesday | 1.6 | 0.122 |
| Thursday | 1.4 | 0.191 |
| Friday | 0.9 | 0.361 |
| **Saturday** | 2.6 | **0.019** |
| Sunday (DST) | -1.6 | 0.121 |

The increase in accidents on Monday is significant, as is Tuesday and
Saturday. Sunday is the only day that trends lower (matching the plot), but
not significantly.

So daylight savings time causes more accidents, but those of us in California
might be in luck! State Assembly member [Kansen Chu][chu] has introduced a
bill to [finally do away with DST][ab-385]! Hopefully it will pass and let us
all get that hour of sleep we deserve.

Large diffs are not rendered by default.

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