MURPHY'S LAW SPECIAL ISSUE Readers of The Sum can now take part in the biggest-ever study of Murphy's Law - "If something can go wrong, it will". Performed by thousands of students across the country, experiments unveiled in this issue of The Sum should finally reveal the truth behind the most notorious version of the law: "If toast can land butter-side down, it will do".

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Issue 7 - February 2001

The three experiments were conducted by a total of 1,005 pupils in the UK (694 in primary schools, 311 in secondary schools)

Experiment 1: Does buttered toast tend to land butter-down ?

 Total number of drops: Total number of butter-down landings: Rate of butter-down landings: 9821 6101 62.1% = 12% higher than chance

To find out if this 12 per cent difference is statistically significant, we can calculate its "p-value" - that is, the chances of getting at least as big a difference as that observed just by fluke. This probability turns out to be extremely low (p ~ 10-127) Thus the 62 per cent rate is both substantially, and statistically significantly, different from the rate expected by chance alone.

Experiment 2: Is butter the cause ?

Results

 Total number of drops: Total number of "B"-down landings: Rate of "B"-down landings: 9748 5663 58.1% = 8 % higher than chance and 4% lower than buttered toast

Again, statistical significance tests against the null hypothesis of a 50:50 split gives an extremely low p-value (~ 10-57). Toast with just a "B" on it thus still lands face-down at a rate substantially, and statistically significantly, different from value expected by chance alone.

Experiment 3: Is height the cause ?

Results

 Total number of drops: Total number of "B"-down landings: Rate of "B"-down landings: 2038 953 46.8% = 3 % lower than chance and 15% lower than buttered toast

Statistical analysis

Both these differences are statistically significant (p = 0.003 and 10-37 respectively).

So increasing drop height to 2.5 metres gives a substantially and statistically significantly higher probability of producing a butter-up landing.

Conclusions

1. Toast really does have a tendency to land butter-side down.
2. The presence of butter is not the major cause of butter-side down landings.
3. The principal cause is height: toast falling from waist-height does not have enough time to come butter-side up again.

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