Refer to Exercise 10.3.8. Suppose the data for fictitious tree species, A and B, were as presented in the accompanying table. The value of the chi-square statistic for this contingency table is χ2s = 9.07. As in Exercise 10.3.8, test the null hypothesis of independence and interpret your conclusion in terms of attraction or repulsion between the species.

Exercise 10.3.8
An ecologist studied the spatial distribution of tree species in a wooded area. From a total area of 21 acres, he randomly selected 144 quadrats (plots), each 38 feet square, and noted the presence or absence of maples and hickories in each quadrat. The results are shown in the table.

The value of the chi-square statistic for this contingency table is χ2s = 7.96. Test the null hypothesis that the two species are distributed independently of each other. Use a non directional alternative and let α = 0.01. In stating your conclusion, indicate whether the data suggest attraction between the species or repulsion. Support your interpretation with estimated conditional probabilities from the data.

Transcribed Image Text:

Species A Present Absent 10 Species B Present 30 Absent 49 Maples Present Absent Hickories Present26 63 Absent 29 26