Wilder and Rypstra (2004) examined the effect of praying mantis excrement on the behavior of wolf spiders to test whether cues from an introduced predator (the praying mantis) would change the movement rate of the native wolf spider. They put 15 wolf spiders in individual containers; inside each container there were two semicircles of filter paper. One semicircle was smeared with praying mantis excrement and one circle was without excrement. The researchers observed each spider for one hour, and calculated spider mean walking speed while it moved across first the excrement circle and then the non-excrement circle. (Each of the 15 spiders did both treatments, with the same spider doing each treatment in each of the 15 containers). Data were modified and are not the original true data.
- Can you conclude with 95% confidence that mean spider walking speed differed based on the presence of the predator cue (praying mantis excrement)? Show your calculations.
| spider# |
cm/sec no excrement |
cm/sec with excrement |
| 1 |
2.5 |
0.4 |
| 2 |
6.5 |
1.9 |
| 3 |
1.1 |
1.2 |
| 4 |
2.7 |
2.6 |
| 5 |
2.9 |
4.4 |
| 6 |
1.6 |
0.3 |
| 7 |
3.2 |
1 |
| 8 |
4.5 |
1.5 |
| 9 |
5 |
3.3 |
| 10 |
5.9 |
2.6 |
| 11 |
2.2 |
0.7 |
| 12 |
1.9 |
1.4 |
| 13 |
3.8 |
2.1 |
| 14 |
3.5 |
3.4 |
| 15 |
5.7 |
2.3 |