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
6	7	7
10	10	4
12	3	4
6	4	3
12	7	4
8	5	2

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

Answer 1

Source of Variation	ss	df	ms	F
between group	76	2	38	6.79
within group(error)	84	15	5.60
total	160	17

Now Tukey HSD Post Hoc Test

We have 3 treatments

Degree of freedom for the error terms is 15

Critical values of the Studentized Range QQ statistic at 5 % level of significance:

Q_0.05,3,15 = 3.6719

Treatment Pair	Tukey HSC Q Statistic	Tukey HSC P value	Inference
0 vs 0.5	3.1053	0.1043221	insignificant
0 vs 1	5.1755	0.0061652	significant
0.5 vs 1	2.0702	0.3356018	insignificant

So on comaparing the calculated value of Q statistic with the observed one we get

Recall following no delay was not significantly different from recall following a half second delay.

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

Recall following half a second delay was not significantly different from recall following a one second delay.