40 Subarctic plant study. The traits of seed-bearing plants indigenous to subarctic Finland were studied in Arctic, Antarctic, and Alpine Research (May 2004). Plants were categorized according to type (dwarf shrub, herb, or grass), abundance of seedlings (no seedlings, rare seedlings, or abundant seedlings), regenerative group (no vegetative reproduction, vegetative reproduction possible, vegetative reproduction ineffective, or vegetative reproduction effective), seed weight class (0–.1, .1–.5, .5–1.0, 1.0–5.0, and

5.0 milligrams), and diaspore morphology (no structure, pappus, wings, fleshy fruits, or awns/hooks). The data on a sample of 73 plants are saved in the SEEDLING file.

a. A contingency table for plant type and seedling abundance, produced by MINITAB, is shown below. ( Note:

NS = no seedlings, SA = seedlings abundant, and SR

= seedlings rare.) Suppose you want to perform a chisquare test of independence to determine whether seedling abundance depends on plant type. Find the expected cell counts for the contingency table. Are the assumptions required for the test satisfied?

b. Reformulate the contingency table by combining the NS and SR categories of seedling abundance. Find the expected cell counts for this new contingency table. Are the assumptions required for the test satisfied?

c. Reformulate the contingency table of part b by combining the dwarf shrub and grasses categories of plant type.
Find the expected cell counts for this contingency table.
Are the assumptions required for the test satisfied?

d. Carry out the chi-square test for independence on the contingency table you came up with in part c , using a = .10. What do you conclude?

Transcribed Image Text:

Tabulated statistics: Abundance, Type Rous: Abundance Columns: Type DwarfShrub Grasses Herbs All NS SA SR All Cell Contents: 3 1 1 5 5 14 32 51 5 2 10 17 13 17 43 73 Count