Sunday 5 March 2017

Assignment



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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