CRJ 310 In-Class Exercise (Z Scores)Name
Nineteen students took the first exam. The mean score of the sample was 76 points on a 0-100 scale, with
a standard deviation of 10 points. You scored 79 points. Assuming that the distribution of these exam
scores was normal, so what was your percentile rank?
Step 1: Identify the Z formula and calculate the Z score.
X-X
Z
2=
다
Do 2=
79-76 -3
5
o
to
10
=0.3
Step 2: Find the corresponding probability from the Z Table based on the calculated Z score.
Step 3: Draw a graph to identify the area of interest.
Step 4: Determine your percentile rank.
CRJ 310 Homework Assignment 3 (Due 10/11/2019 in class)
Your Name
Homework Assignment 3 has two parts: (1) Part 1 consists of the following 5 questions and (2) Part 2 has 10
online questions that are available on Blackboard. For Part 2 questions, please click on Course Content –>
Module 2 (for Exam II) –> Exams/Homework Assignments/Chapter Practices –> Homework #3 Part 2. A
late assignment will incur a reduction of 1 point for each day it is late, including the due date.
A criminologist developed a test to measure recidivism, where low scores indicated a lower probability of
repeating the undesirable behavior. The test is normed so that it has a mean of 140 and a standard deviation
of 40 based on a sample of 300. Please also round Z-scores to TWO decimal places (e.g., 1.75).
1. Identify the formula used to calculate a z-score. Make sure that you distinguish the formula based on the
sample information from the formula based on the population information and find the correct one. (Bonus)
2. John Doe has a score 130. What is his percentile rank? Also draw a graph to identify the area of interest
and use a sentence to explain what your answer means based on the above hypothetical case.
3. What percentage of scores falls between 105 and 158? Also draw a graph to identify the area of interest
and use a sentence to explain what this percentage means.
4. What percentage of respondents should score above 186? Also draw a graph to identify the area of
interest and use a sentence to explain what this proportion means.
5. Based on your answer from Question 4 and the sample size, how many respondents should score above
186? Use a sentence to explain what your answer means.
