Next section: Formal model

The degrees of freedom for the t is equal to the degrees of freedom error in the analysis of variance which is: N - a = 40 - 4 = 36. A t table can be used to find that the probability value (p) is less than .0001. Therefore, the decrease in running time associated with the increase in magnitude of reward is significant. Rats run faster if the reward is larger.

The quadratic component of trend is used to test whether the decreasing slope that shows up as a flattening out of the function is significant. The table on a previous page shows that the coefficients for the quadratic component of trend with four groups are: 1, -1, -1, 1.

L = ΣM

s

t = 3/1.414 = 2.12,

df = 36, and p = .041. The quadratic component of trend is significant.

Next section: Formal model