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
10	10	7
4	4	4
9	6	2
11	5	4
6	3	3
8	8	4

(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.)

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

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

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

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

Answer 1

(a)

		ANOVA
SOURCE		SS	DF	MS	F
BETWEEN groups		48.00	2	24	4.39
WITHIN groups(ERROR)		82.00	15	5.47
TOTAL		130.00	17

					within SS		between SS
Group	nj	mean(xj-)	s2	nj*xj-	(n-1)s2	(xj--x-)	nj(xj--x-)2
0	6	8	6.8	48	34	2	24
0.5	6	6	6.8	36	34	0	0
1	6	4	2.8	24	14	-2	24
sum	18	18	16.4	108	82	0	48
grand mean(x-)	6

(b1)The critical value is 3.89  for each pairwise comparison

Since the number of replication for each of the treatments is equal=6, so critical value for each pairwise comparison will be same.

Tukey HSD=	q*sqrt((MSE/2)*(1/n1+1/n2)=	3.89
q(0.05, 3,15)=	4.08
MSE=	5.47
n1=	6
n2=	6

(b2) right choice is last

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

pair wise	difference	HSD	Remarks
0-0.5	2	3.89	non significant
0-1	4	3.89	significant
0.5-1	2	3.89	non significant

since difference between 0 and 1 is more than HSD, so these pairwise comparison is significantly different to each other