Executives learn Spanish. The table below gives the pretest and posttest scores on the MLA listening test in Spanish for 20 executives who received intensive training in Spanish.

12 The setting is identical to the one described in Example 7.7

(page 405). DATADATA DATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATADATADATA DATADATADATA DATADATADATADATADATA DATA FILE SPANISH Subject Pretest Posttest Subject Pretest Posttest 1 30 29 11 30 32 2 28 30 12 29 28 3 31 32 13 31 34 4 26 30 14 29 32 5 20 16 15 34 32 6 30 25 16 20 27 7 34 31 17 26 28 8 15 18 18 25 29 9 28 33 19 31 32 10 20 25 20 29 32

(a) We hope to show that the training improves listening skills.

State an appropriate H0 and Ha. Describe inwords the parameters that appear in your hypotheses.

(b) Make a graphical check for outliers or strong skewness in the data that you will use in your statistical test, and report your conclusions on the validity of the test.

(c) Carry out a test. Can you reject H0 at the 5% significance level? At the 1% significance level?

(d) Give a 90% confidence interval for the mean increase in listening score due to the intensive training.