1. For a distribution of scores, X = 40 corresponds to a zscore of z =
+1.00, and X = 28 corresponds to a zscore of z = -0.50. What are the values for
the mean and standard deviation for the distribution? (Hint: Sketch a
distribution and locate each of the zscore positions.)
Solution: we know Z=(x-µ)/𝞼 then we get x=µ+𝞼Z…..(1)
For X=40 and Z=1 we get from (1) , 40=µ+𝞼…………(2)
For X=28 and
Z=-0.50 we get from (1), 28=µ-0.50*𝞼…………(3)
Subtracting (3)
from (2) we get 40-28=µ+𝞼- µ+0.50*𝞼=1.50𝞼
ð
12=1.50𝞼
ð
𝞼=8.
ð
Putting 𝞼=8 in equation (2) we get µ=40-8=32
ð
Hence the mean µ=32 and standard deviation 𝞼=8
3. For a normal distribution,
a. What z-score
separates the highest 10% from the rest of the scores?
Solution:Z-scores separates the highest 10% from the
rest of the scores is 1.282
b. What z-score
separates the highest 30% from the rest of the scores?
Solution: Z-scores separates the highest 30% from
the rest of the scores is 0.5244.
c. What z-score
separates the lowest 40% from the rest of the scores?
Solution: Z-scores separates the highest 40% from
the rest of the scores is -0.253
d. What z-score
separates the lowest 20% from the rest of the scores?
Solution: Z-scores separates the highest 20% from
the rest of the scores is -0.8416
4. A population consists of the following N = 10 scores: 0, 6, 4, 3, 12, 6,
7, 5, 1, 11
Your task is to enter the data for this variable into SPSS, use the
descriptives command to do a z-transformation of the whole distribution into a
standardized distribution, and then get the frequencies with mean and standard
deviation for both the original raw scores distribution and the standardized
distribution. Attach the printout with the frequencies to this homework.
Statistics
|
|
esteem
|
Zscore(esteem)
|
N
|
Valid
|
10
|
10
|
Missing
|
0
|
0
|
Mean
|
5.5000
|
.0000000
|
Std. Error of Mean
|
1.22247
|
.31622777
|
Median
|
5.5000
|
.0000000
|
Mode
|
6.00
|
.12934
|
Std. Deviation
|
3.86580
|
1.00000000
|
Variance
|
14.944
|
1.000
|
Skewness
|
.404
|
.404
|
Std. Error of Skewness
|
.687
|
.687
|
Kurtosis
|
-.357
|
-.357
|
Std. Error of Kurtosis
|
1.334
|
1.334
|
Range
|
12.00
|
3.10414
|
Minimum
|
.00
|
-1.42273
|
Maximum
|
12.00
|
1.68141
|
Sum
|
55.00
|
.00000
|
esteem
|
|
Frequency
|
Percent
|
Valid
Percent
|
Cumulative
Percent
|
Valid
|
.00
|
1
|
10.0
|
10.0
|
10.0
|
1.00
|
1
|
10.0
|
10.0
|
20.0
|
3.00
|
1
|
10.0
|
10.0
|
30.0
|
4.00
|
1
|
10.0
|
10.0
|
40.0
|
5.00
|
1
|
10.0
|
10.0
|
50.0
|
6.00
|
2
|
20.0
|
20.0
|
70.0
|
7.00
|
1
|
10.0
|
10.0
|
80.0
|
11.00
|
1
|
10.0
|
10.0
|
90.0
|
12.00
|
1
|
10.0
|
10.0
|
100.0
|
Total
|
10
|
100.0
|
100.0
|
|
Zscore(esteem)
|
|
Frequency
|
Percent
|
Valid
Percent
|
Cumulative
Percent
|
Valid
|
-1.42273
|
1
|
10.0
|
10.0
|
10.0
|
-1.16405
|
1
|
10.0
|
10.0
|
20.0
|
-.64670
|
1
|
10.0
|
10.0
|
30.0
|
-.38802
|
1
|
10.0
|
10.0
|
40.0
|
-.12934
|
1
|
10.0
|
10.0
|
50.0
|
.12934
|
2
|
20.0
|
20.0
|
70.0
|
.38802
|
1
|
10.0
|
10.0
|
80.0
|
1.42273
|
1
|
10.0
|
10.0
|
90.0
|
1.68141
|
1
|
10.0
|
10.0
|
100.0
|
Total
|
10
|
100.0
|
100.0
|
|
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