Question

Iconic memory is a type of memory that holds visual information for about half a second (0.5 seconds). To demonstrate this type of memory, participants were shown three rows of four letters for 50 milliseconds. They were then asked to recall as many letters as possible, with a 0-, 0.5-, or 1.0-second delay before responding. Researchers hypothesized that longer delays would result in poorer recall. The number of letters correctly recalled is given in the table.

Delay Before Recall
0	0.5	1
9	4	7
8	5	2
10	5	4
5	9	4
6	3	2
10	10	5

(a) Complete the F-table. (Round your values for MS and F to two decimal places.)

Source of Variation	SS	df	MS	F
Between groups
Within groups (error)
Total

(b) Compute Tukey's HSD post hoc test and interpret the results. (Assume alpha equal to 0.05. Round your answer to two decimal places.)

The critical value is _____ for each pairwise comparison.

Which of the comparisons had significant differences? (Select all that apply.)

a) The null hypothesis of no difference should be retained because none of the pairwise comparisons demonstrate a significant difference.

b) Recall following a half second delay was significantly different from recall following a one second delay.

c) Recall following no delay was significantly different from recall following a half second delay.

d) Recall following no delay was significantly different from recall following a one second delay.

Answer 1

Applying one way ANOVA: (use excel: data: data analysis: one way ANOVA: select Array):

Source	SS	df	MS	F
Between	48.00	2	24.00	4.50
Within	80.00	15	5.33
Total	128.00	17

pooled standard deviation        =Sp =√MSE      =	2.309
critical q with 0.05 level and at k=3 and N-k=15 degree of freedom=		3.67
Tukey's (HSD) for group i and j =                  (q/√2)*(sp*√(1/ni+1/nj)         =		3.46

d) Recall following no delay was significantly different from recall following a one second delay.