PSYC 354
SPSS HOMEWORK: CENTRAL TENDENCY
Problem Set 1: A neuropsychologist assesses the cognitive functioning of 17 adults who are at-
risk for Alzheimer’s disease using the Mini-Mental State Examination (MMSE). Scores higher
than 24 indicate better cognitive functioning, while scores lower than 24 indicate worse
functioning and possible early-stage Alzheimer’s disease. The scores are contained in the table
below. Remember to put your initials within any and all variable names.
MMSE Scores
26
29
29
8
29
24
10
28
28
27
29
28
27
26
30
29
26
1. Using the data in the table above, set up a data file in SPSS and create a table of
descriptive statistics using the “Explore” command. Paste the table here: (8 pts)
Descriptives
Statistic Std. Error
MMSE_SCORES
_KS
Mean 25.4706 1.55090
95% Confidence Interval
for Mean
Lower Bound 22.1828
Upper Bound 28.7583
5% Trimmed Mean 26.1895
Median 28.0000
Variance 40.890
Std. Deviation 6.39451
Minimum 8.00
Maximum 30.00
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Range 22.00
Interquartile Range 3.00
Skewness -2.349 .550
Kurtosis 4.610 1.063
2. Using the same data, create a histogram showing the distribution of MMSE scores in the
sample. Paste the histogram here: (7 pts)
3. List the mean and the median for MMSE scores. (4 pts)
Mean is equal to 25.47.
Median is equal to 28.0000.
4. Based on the information in numbers 1-3, which measure of central tendency would you
use to describe this data set? Support your answer with material from the presentations
and/or reading this week. (6 pts)
PSYC 354
Due to skewed data and the mean being “unreliable” or pulled away from the center, the
median proves to be a much better form of the central tendency in which to describe this data set.
5. Locate any outliers (scores that are more extreme than the rest of the data). Based on your
knowledge of MMSE scores from the scenario, are there any patients you would
recommend for further evaluation for Alzheimer’s? If so, how many? Explain your
reasoning. (5 pts)
The outliers for this data set would be the scores of 8 and 10, so two patients would be
recommended for further evaluation for Alzheimer's. This would be because scores lowers than
24 indicate worse functioning and possibly early stages of Alzheimer's disease and score of 8 and
10 are much lower than 24.
Problem Set 2: A forensic psychologist wants to examine the level of narcissistic personality
traits in those who are diagnosed with antisocial personality disorder (ASPD) and those who do
not qualify for ASPD within a local prison population. She administers a measure of narcissistic
personality traits where higher scores indicate higher levels of narcissism and scores range from
0–35. Name your variables in Variable View. Assign values to the “Diagnosis” variable as
follows: 1 = ASPD; 2 = no ASPD. Remember to put your initials within any and all variable
names.
1
Diagnosis
2
Narcissism
Score
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
34
2
28
30
29
4
35
34
34
32
12
8
12
12
6
5
8
9
10
PSYC 354
2 6
1. Using the data in the table above, set up your data file in SPSS and create one table
of Descriptive Statistics using the “Explore” function that shows descriptives for
narcissism split by group (ASPD and no ASPD separately). Paste the table here: (7
pts)
Descriptive
Diagnosis_KS Statistic
Std.
Error
Narcissim_Sc
ores_KS
ASPD Mean 26.2000 3.94067
95% Confidence
Interval for Mean
Lower
Bound
17.2856
Upper
Bound
35.1144
5% Trimmed Mean 27.0556
Median 31.0000
Variance 155.289
Std. Deviation 12.46150
Minimum 2.00
Maximum 35.00
Range 33.00
Interquartile Range 12.00
Skewness -1.631 .687
Kurtosis 1.131 1.334
NO
SPD
Mean 8.8000 .84063
95% Confidence
Interval for Mean
Lower
Bound
6.8984
Upper
Bound
10.7016
5% Trimmed Mean 8.8333
Median 8.5000
Variance 7.067
Std. Deviation 2.65832
Minimum 5.00
PSYC 354
Maximum 12.00
Range 7.00
Interquartile Range 6.00
Skewness .002 .687
Kurtosis -1.503 1.334
2. What is the standard deviation for the ASPD group in this sample? (5 pts)
The standard deviation for the ASPD group is 12.46150.
3. Compare the means of each group (ASPD and no ASPD). What can you say about the
narcissism scores of the ASPD group compared to the no ASPD group? (5 pts)
The means of those who were diagnosed with ASPD (their mean is 26.2)is a lot higher than those
with no ASPD (their mean is 8.8) which indicates that the distribution with be a skewed one
4. Using the same data, create a boxplot in SPSS to show the difference in narcissism scores
between the two diagnostic groups. Paste the boxplot here: (7 pts)
5. Locate the outliers for the ASPD group in the boxplot. (Outliers are depicted by dots that
lie farther away from the rest of the data. The numbers next to the dots represent the row
number in your data set where that score lies.) What effect do these data points have on
the mean narcissism score for the ASPD group? (6 pts)
PSYC 354
These outliers have higher narcissism scores compared to the central tendency of the data for the
ASPD group. Since outliers are extreme values, they can have a significant impact on the mean
by pulling it higher than it would be if these points were closer to the median. This effect could
give a somewhat distorted view of the central tendency of narcissism scores within the ASPD
group, making the average appear higher than it might be if those outliers were excluded.
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