# Homing in Limpets - Statistical analysis watch

1. Hi,
I have recently carried out a field investigation on homing behaviour of limpets. My hypothesis was that limpets placed more than 10 cm from base do not return. I placed 3 no at each 6,9,12 and 15 cm from base on rocks at low tide . I came back next day at low tide to check. One at 6 cm and two at 9 cm returned to base. Two at 12 cm went further away from base. The rest got lost, washed away etc.

I am looking for guidance on any statistical tests to use ( chi test, f test, t test, others) to show if my hypothesis has been proven true. I am totally confused what, if any, test is relevant. Any help and guidance will be greatly appreciated . I have searched web but ended up totally lost ! Thanks
2. One possible idea, which I'm not saying is 100% correct, but should work:

Model the place where you placed the limpets as 0 and then each cm movement back towards home as +1 and each cm away from home as -1.
This will then give you a score for each limpet in terms of their movement and a score for each set. You would have to score the lost ones as 0.
Then you can use the t test to see whether there is a statistically significant difference between each pair. So you could test for a difference between the ones placed at 6 and 9, a difference between the ones placed at 9 and 12 and so on.
3. Thank you for the help.
4. Hi,
I have tried to apply the paired t-test but still not clear on certain points. Can anyone guide plse.

Is this correct paired T-Test : The difference between the observations is calculated for each pair, and the mean and standard error of these differences are calculated. Dividing the mean by the standard error of the mean yields a test statistic, ts, that is t-distributed with degrees of freedom equal to one less than the number of pairs.
----- using the ts value and degrees of freedom, I can get a P value. P = 0, no difference, P=1 big difference ---

Here is problem I am having :
- Should the pairing exclude those washed away ?
- should differences between observations in the pairing be only positive? some pairings give negative values.
- Once I have a P value, how can I relate it to my hypothesis ?

Many Thanks .

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Updated: March 5, 2010
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