School

Florida Atlantic University **We aren't endorsed by this school

Course

PSY 3215

Subject

Statistics

Date

Sep 25, 2023

Type

Other

Pages

6

Uploaded by UltraRabbitMaster894 on coursehero.com

Name: Ann-Koraly Jean-Bart
Homework #3: ANOVA and Post-Hoc LSD (worth 35 points)
Instructions: Read the scenario and answer the questions. Print out one copy to turn in and print
another copy to check during class. In addition to this document, you should turn in:
All relevant SPSS outputs
Word document with write up
Figure (either from Excel or pasted into this Word document)
A researcher is interested in how long people can retain information in short term memory. He makes a
list of three-letter strings (for example "GSZ" is a letter string) with 50 items on it. He randomly assigns
40 participants into one of four memory conditions: 3 seconds, 5 seconds, 7 seconds and 9 seconds. In
the 3 second memory condition, participants try to recall the letter string 3 seconds after seeing it on a
screen; in the 5 second condition, they wait 5 seconds before recalling, and so forth. Participants were
told not to repeat the letters silently to themselves. The number of correctly recalled letter strings (out of
50) was recorded for each participant. The data can be found in the Excel file "Memory.xlsx".
1). Check assumptions in SPSS using histograms and box plots. Are any assumptions violated?

- Assumptions:
Normality and homogeneity of variance were assessed by examining histograms and box plots for each of the
dependent variables. This revealed that variable memory had a slightly non-normal distribution. Because ANOVA is
robust to violations of normality, the analysis was conducted on the non-transformed variable. Visual inspection did
not indicate a violation of homogeneity of variance. There were also several outliers present in the data; these cases
were 14 and 18.
2). Run the ANOVA in SPSS.
Tests of Between-Subjects Effects
Dependent Variable:
memory
Source
Type III Sum of
Squares
df
Mean Square
F
Sig.
Corrected Model
785.075
a
3
261.692
10.984
.000
Intercept
21022.225
1
21022.225
882.360
.000
conditions
785.075
3
261.692
10.984
.000
Error
857.700
36
23.825
Total
22665.000
40
Corrected Total
1642.775
39
3). Fill in the source table using information from your SPSS output.
SOURCE
SS
df
MS
F
p
BG
785.075
3
261.692
10.984
<.000
WG
857.700
36
23.825
TOTAL
1642.775
39
ANSWER QUESTION:
Did the researcher reject the null hypothesis?
(yes or no) ________
4). Calculate the LSD by hand and answer the questions that follow (SHOW ALL WORK; YOU CAN
CHECK YOURSELF IN EXCEL OR SPSS):

df error =
tcrit (df error)
MS error =
s =
LSD = _______
Mean Comparisons:
-Mean
3 sec
vs. Mean
9 sec
= |
| = ______
Greater than (>) LSD value? __
Significant?__
___
Mean
3 sec
vs. Mean
7 sec
= |__
_| =
_____
Greater than (>) LSD value?
___
__
Significant?__
__
Mean
sec
vs. Mean
5 sec
= |__
__
___| =
_____
Greater than (>) LSD value? _
__
Significant?__
__
5). Run LSD and Bonnferoni post hoc tests in SPSS.
Multiple Comparisons
Dependent Variable:
memory
(I) conditions
(J) conditions
Mean Difference
(I-J)
Std. Error
Sig.
95%
Confidence
Interval
Lower Bound
LSD
3 seconds
5 seconds
.6000
2.18289
.785
-3.8271
7 seconds
5.5000
*
2.18289
.016
1.0729
9 seconds
11.0000
*
2.18289
.000
6.5729
5 seconds
3 seconds
-.6000
2.18289
.785
-5.0271
7 seconds
4.9000
*
2.18289
.031
.4729
9 seconds
10.4000
*
2.18289
.000
5.9729
7 seconds
3 seconds
-5.5000
*
2.18289
.016
-9.9271
5 seconds
-4.9000
*
2.18289
.031
-9.3271
9 seconds
5.5000
*
2.18289
.016
1.0729
9 seconds
3 seconds
-11.0000
*
2.18289
.000
-15.4271