16. A cognitive psychologist wanted to test the effects of practice on language skills. The number of errors made by 20 students learning French was compared at the beginning and end of the semester using the same language test. Test whether errors decreased significantly across time. The mean of the difference scores (T2-T1) was found to be MD= -12 with a SEM=3.01

a. State the null and alternative hypotheses. Is it 1 tailed or 2?

b. Find the critical value for this t-test. Which tail is shaded?

c. Perform a paired samples t test (calculations are easy here)

d. Is there a significant difference between the two conditions? Test using an alpha level of .05, using the direction of the test that is listed in the question.

Write your conclusion using APA format (test used, significance, include IV and DV, APA stats and direction of any difference found.)