When studying animal behavior, the distribution of organisms within a choice chamber can be studied to identify animal preferences. 20 Isopods are placed in a 2-choice choice chamber. A cotton ball dampened with distilled water is placed in Chamber A; A dry cotton ball is placed in Chamber B. After 15 minutes 2 Isopods are located in Chamber B, and 18 isopods are found in Chamber A. Perform the chi-squared test to determine if the distribution of isopods is significant or due to random chance. a. chi-squared is 1.20, no it is not significant. b. chi-squared is 8.42, no its not significant. c. chi-squared = 12.8, yes it is significant. d. chi-squared is 18.59, yes it is significant.

The correct option is c. chi-squared = 12.8, yes it is significant.

Explanation:

Available data:

H₀= Individuals will be equally distributed  

H₁ = Individuals will not be equally distributed.  

∑ is the sum of the terms

O are the Observed individuals: 2 in chamber B, and 18 in chamber A.  

E are the Expected individuals: 10 in each chamber  

X² = ∑ ((O-E)²/E) = ((2 - 10)²/10) + ((18 - 10)²/10) = 6.4 + 6.4 = 12.8  

X² = 12.8  

(K = Independent variables = dry cotton and wet cotton)  

12.8 > 3.84 meaning that the difference between the observed individuals and the expected individuals in each chamber is statistically significant. Not probably to occur by random chances.  

the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.