Question

1. 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. (3 points)

Answer 1

Answer:

The distribution  of isopods is statistically significant.

Explanation:

H₀= Individuals will be equally distributed

H₁ = Individuals will not be equally distributed.  

• Chi square= ∑ ((O-E)²/E)  

∑ 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

• Freedom degrees = K – 1 = 2 - 1 = 1  

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

• Significance level, 5% = 0.05  

• Table value/Critical value = 3.84

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

There is enough evidence to reject the null hypothesis.