Gagn and Gagnier (2004) studied the classroom behavior of children who were a year younger than their

Gagné and Gagnier (2004) studied the classroom behavior of children who were a year younger than their classmates and those who were a typical age for their grade. The children’s teachers rated each student’s classroom conduct, with higher numbers indicating better behavior. The researchers found that the younger students had a mean score of 15.92 (SD = 5.33, n = 98). The students who were the typical age for their grade had a mean score of 15.01 (SD = 5.85, n = 1,723).

a. Explain why an unpaired-samples t-test is appropriate for these data.

b. What is the null hypothesis for these data?

c. What is the α for this example?

d. Several experts on grade skipping and early entrance to school recommend that a child be younger than their classmates only if the child already is well behaved. Given this knowledge, is a one- or a two-tailed hypothesis appropriate for this NHST? Justify your response.

e. Given your response to item (d), what is the appropriate alternative hypothesis for this example?

f. Calculate the degrees of freedom for the data.

g. Find the tcrit value.

h. Calculate the pooled standard deviation and the pooled variance for these data.

i. Calculate the tobs value for the data.

j. Should you reject or retain the null hypothesis?

k. Find a p-value for this example.

l. Should you worry about Type I or Type II error in this example?

m. Calculate and interpret Cohen’s d for this example.

n. Do the data in this example violate any assumptions? If so, which one(s)?