2. A developmental psychologist was interested in the development of language in children. He wondered how children of different age groups vary in verb knowledge. He measured the total number of verbs in the vocabulary of sixty-three children in three different age groups and obtained the following data. Test for a difference at alpha = .05.

Age Class of Child

19 months24 months29 months

Means 1.99 20.01 19.99

Standard dev. .78 1.10 1.13

n's 11 11 11

STEP 1: State the null and alternative hypotheses in words. (2 points)

STEP 2: Set up the criteria for making a decision. That is, find the critical value.

(1 point)

STEP 3: Compute the appropriate test-statistic. SHOW YOUR WORK!

(3 points)

Source SS df MS F

Between (group)___ ___ 2.00 ___

Within (error) ___ ___ ___

Total 40.51 ___

STEP 4: Evaluate the null hypothesis (based on your answers to the above steps).

(Circle One) REJECT FAIL TO REJECT (1 point)

STEP 5: Based on your evaluation of the null hypothesis, what is your conclusion?

(1 point)

STEP 6: Calculate the least-biased estimate of the magnitude of effect on the

ANOVA you calculated above. (2 points)

STEP 7: Interpret the answer you got in step #6 above. (1 point)