PSY-380 Week 1 Homework 1 In an experiment, researchers measure two types of variables: independent and dependent variables

1. In an experiment, researchers measure two types of variables: independent and dependent variables.

(a) Which variable is measured in each group?

• independent variable
• dependent variable

(b) Which variable is manipulated to create the groups?

• independent variable
• dependent variable
1. A qualitative variable varies by ____________ ; a quantitative variable varies by ________

1. State whether each of the following words best describes descriptive statistics or inferential statistics.

(a) summarize

• descriptive statistics
• inferential statistics

(b) infer

• descriptive statistics
• inferential statistics

(c) describe

• descriptive statistics
• inferential statistics
1. To determine whether a new sleeping pill was effective, adult insomniacs received a pill (either real or fake), and their sleeping times were subsequently measured (in minutes) during an overnight observation period.

(a) Identify the dependent variable in this study.

• sleeping pill (real or fake)
• number of insomniacs
• time spent sleeping
• number of observation periods

(b) Identify the independent variable in this study.

• sleeping pill (real or fake)
• number of insomniacs
• time spent sleeping
• number of observation periods
1. Researchers are interested in studying whether personality is related to the month in which someone was born.

(a) Is it appropriate to code the data? Explain.

____________ to numerically code “months” because it is _________ scale variable.

(b) What scale of measurement is the month of birth?

• ordinal
• ratio
• interval
• nominal
1. State whether each of the following are continuous or discrete data.

(a) time in seconds to memorize a list of words

• Continuous
• Discrete

(b) number of students in a statistics class

• continuous
• discrete

(c) the weight in pounds of newborn infants

• continuous
• discrete

(d) the SAT score among college students

• continuous
• discrete
1. Szklarska, Koziel, Bielicki, and Malina (2007) hypothesized that taller young men are more likely to move up the scale of educational attainment compared with shorter individuals from the same social background. They recruited 91,373 nineteen-year-old men to participate in the study. Do these participants most likely represent a sample or population? Explain.
2. Researchers often prefer to report cumulative percents from the bottom up to explain how certain scores rank at or below other scores in a distribution. What is this type of summary called?
• an open interval
• a distribution summary
• a cumulative frequency
• a percentile rank
• a lower boundary
1. Below is the number of times a commercial was shown displaying high fat, high sugar foods during children’s programming over each of 20 days.

5, 21, 9, 7, 10, 14, 12, 3, 11, 7, 8, 10, 16, 22, 18, 19, 21, 11, 6, 17

(a) Create a simple frequency distribution for these grouped data with four intervals.

Interval          Frequency

18-22

13-17

8-12

3-7

(b) Which interval had the largest frequency?

• Interval: 18-22
• Interval: 13-17
• Interval: 8-12
• Interval: 3-7
1. The upper boundaries for a distribution of waiting times (in seconds) in a grocery store aisle are 43, 54, 65, and 76. List the value for each lower boundary in this distribution.
 Lower Boundary Upper Boundary 76 65 54 43
1. A researcher records the number of dreams that 50 college freshman students recalled during the night prior to a final exam.

(a) Convert this table to a percentile rank distribution.

 Number of Dreams Cumulative Frequency Percentile Rank 4 50 % 3 45 % 2 28 % 1 18 % 0 7 %

(b) What is the number of dreams at the 56th percentile?
dreams

1. Organize the following data into a stem-and-leaf display where the following is true. (Enter numbers from smallest to largest separated by spaces. Enter NONE for stems with no values.)

173, 240, 179, 118, 240, 174, 245, 242, 179, 171

176, 248, 247, 116, 113, 112, 244, 115, 110, 175

(a) the stem has one digit

 Stem Leaf 1 2

(b) the leaf has one digit

 Stem Leaf 11 17 24

1. The following is an incomplete simple frequency distribution table for the number of mistakes made during a series of military combat readiness training exercises.
 Number of Mistakes Frequency 10–A 1 B–9 3 0–4 C N = 19

Find the missing values for A, B, and C.

A =

B =

C =

1. The following bar graph summarizes the number of nights per week a sample of college students spent studying.

(a) How many students were observed in this study? (Enter an exact number.)

(b) How many students studied 3 nights per week? (Enter an exact number.)

(c) How many students studied at least 3 nights per week? (Enter an exact number.)

1. Keith Rollag (2007) noticed that coworkers evaluate and treat “new” employees differently from other staff members. He was interested in how long a new employee is considered “new” in an organization. He surveyed four organizations ranging in size from 34 to 89 employees. He found that the “new” employee status was mostly reserved for the 30% of employees in the organization with the lowest tenure.

(a) In this study, what was the real range of employees hired by each organization surveyed?

(b) What was the cumulative percent of “new” employees with the lowest tenure?

1. In June 2016, a CBS News poll asked a sample of adults nationwide whether it should be legal or not legal for same-sex couples to marry†. The opinions of adults nationwide were as follows: 58% legal; 33% not legal; and 9% unsure/ no answer.

(a) What type of distribution is this?

• simple frequency distribution
• cumulative percent distribution
• cumulative frequency distribution
• relative percent distribution

(b) Knowing that 1,280 adults were polled nationwide, how many Americans polled felt that same-sex couples should be allowed to legally marry? (Round your answer to the nearest whole number.)

Course: PSY-380 Introduction to Probability and Statistics
School: Grand Canyon University

• 01/12/2019
• 150
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