Question

A researcher was interested in learning about the effect of caffeine consumption on problem solving. To examine this relationship, participants were randomly selected and assigned to one of four conditions: no caffeine consumption, 100 mg dosage of caffeine, 200 mg dosage of caffeine, or 300 mg dosage of caffeine. The participants were then asked to solve as many anagrams* as possible in a 5 minute period. The results of the study are presented below.

*Anagrams are word puzzles that are solved by rearranging the letters so that each letter is used exactly once to create a new word, for example: No Eagle in Jail = Angelina Jolie or Balk Tables = Basketball.

No Caffeine Group

3

7

4

4

3

8

8

4

4

7

1

5

3

8

5

6

100 mg Group

6

8

9

8

11

10

7

5

5

8

8

5

7

7

9

7

200 mg Group

3

11

6

6

5

8

6

6

8

8

6

9

7

8

9

6

300 mg Group

6

5

7

6

7

5

9

4

10

8

7

7

9

5

3

6

What is the effect size for this set of data?

Answer 1

Anova: Single Factor
SUMMARY
Groups	Count	Sum	Average	Variance
No Caffeine Group	16	80	5	4.533333
100 mg Group	16	120	7.5	3.066667
200 mg Group	16	112	7	3.6
300 mg Group	16	104	6.5	3.6
ANOVA
Source of Variation	SS	df	MS	F	P-value	F crit
Between Groups	56	3	18.66667	5.045045	0.003493	2.758078
Within Groups	222	60	3.7
Total	278	63

effect size = SSbet / SST = 56/278 = 0.2014 (small )