Seedlings of the parasitic plant Cuscuta pentagona (dodder) hunt by directing growth preferencially toward nearby host plants. Lacking eyes, or even a nervous system, how do they detect their victims? To investigate the possibility that the parasite detects volatile chemicals produced by host plants, Runyon et al. (2006) placed individual dodder seedlings into a vial of water at the center of a circular paper disc. A chamber containing volatile extracts from tomato (a host plant) in solvent was placed at one edge of the disc, whereas a control chamber containing only solvent was placed at the opposite end. The researchers divided the disc onto equal-area quadrats to record in which direction the seedlings grew. Of 30 dodder plants tested, 17 seedlings grew toward the volatiles, 2 grew away (toward solvent), 7 grew towards the left side, and 4 grew toward the right side. The researchers used gas chromatographic analysis to extract and identify eight major volatile chemicals present in the host plants (tomato). They tested each of these chemicals separately using the same experimental designn to determine whether dodder seedlings would preferentially orient their growth. Of 34 dodder plants tested with one of these chemicals, alpha-pinene (also present in pine resin, as its name suggests), 11 seedlings grew toward the volatiles, 6 grew away, 8 grew toward the left side, and 9 grew toard the right side. The authors compared these observed frequencies to those expected by the null hypothesis. Their test statistic was Chi-Squared = 1.53. They obtained P=0.68.

The frequency of dodder plants growing in all four directions is equal. Is this the null or alternate hypothesis?

The frequency of plants growing in all four directions is not equal. Null or alternate?

The following statements are True of False:

The difference between the observed and expected frequencies is statistically significant.

The test statistic exceeds the critical value corresponding to alpha = 0.05

There is no evidence that dodder plants orient their growth toward alpha-pinene.

The difference between the proportion of individuals that grow toward alpha-pinene and that grow away