Exam (elaborations) PSY 520 Topic 2 Exercises 520.docx

TOPIC 2 EXERCISE
1




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Shanice S. Roseborough
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Grand Canyon University: PSY-520
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April 29, 2020
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, TOPIC 2 EXERCISE
2

Chapter 5

5.11 Finding Proportions Scores on the Wechsler Adult Intelligence Scale (WAIS) approximate
a normal curve with a mean of 100 and a standard deviation of 15. What proportion of IQ scores
are WAIS mean = 100; standards deviation = 15

a. Above Kristen’s 125?
µ = 100 ; ơ = 15
X−μ 125−100
z= = = 25/15 => z = 1.67 looking at table A
a
, it gives us a
σ 15
value of C = 0.0475.

b. Below 82
82−100 −18
z= = = -1.2, so z value of -1.2 gives us a C value of 0.1151




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c. Within 9 points of mean




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z = 9/15 = 0.6




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z = (-9)/15 = -0.6, so B value of z = 0.6 is 0.2257, but it can be in positive or negative
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direction so we need to add the two. 0.2257 + 0.2257 = 0.4514
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d. More than 40pts from mean
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z = 40/15 = 2.67 or -2.67
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so if z = 2.67 then c value is 0.0038; but it is asking for more than 40pts so we do 1-
0.0038 = 0.0076. So 0.0076 is the answer.
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5.13 Finding Scores

Mean = 100; standard deviation = 15
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a. Upper 2% to the right and 98% to the left. C = 0.020 and z value is 2.06
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X = µ + z (ơ)
X = 100 + 2.6 (15)
X = 130.90
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b. Lower 10% z= 1.29
x= 100 + (-1.29)(15)
x = 80.65
c. Upper 60% ; which means there is 40% is the other direction; but it is only 10% from 50.
We will use c = 0.10 and z = 1.29 but positive



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