PSY STATS CHAPTER 1

continuous variable

REAL INTERVALS there are an infinite number of possible values that fall between any two observed values. A continuous variable is divisible into an infinite number of fractional parts.

Constructs

are internal attributes or characteristics that cannot be directly observed but are useful for describing and explaining behavior.

Compute (ΣX)2 for the following set of numbers: 5, 9, 8, 4

676

Data (plural)

are measurements or observations

For the following scores, find the value of each expression: X 3 5 0 2 A) EX B) EX^2 C) EX+1 D) E(X+1)

A) EX = 10 B) EX^2 = 38 C) EX+1 = 11 D) E(X+1) = 14

For the following set of scores, find the value of each expression: X 3 2 5 1 3 A) EX^2 B) (EX)^2 C) E(X-1) D) E(X-1)^2

A) EX^2 = 48 B) (EX)^2 = 196 C) E(X-1) = 9 D) E(X-1)^2 = 25

Weinstein, McDermott, and Roediger (2010) conducted an experiment to evaluate the effectiveness of different study strategies. One part of the study asked students to prepare for a test by reading a passage. In one condition, students generated and answered questions after reading the passage. In a second condition, students simply read the passage a second time. All students were then given a test on the passage material and the researchers recorded the number of correct answers. A) Identify the dependent variable for this study. B) Is the dependent variable discrete or continuous? C) What scale of measurement (nominal, ordinal, interval, or ratio) is used to measure the dependent variable?

A. CORRECT ANSWERS B. DISCRETE C. RATIO

In an experiment examining the effects Tai Chi on arthritis pain, Callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. Half of the participants immediately began a Tai Chi course and the other half (the control group) waited 8 weeks before beginning. At the end of 8 weeks, the individuals who had experienced Tai Chi had less arthritis pain that those who had not participated in the course. A. Identify the independent variable for this study. B. What scale of measurement is used for the independent variable? C. Identify the dependent variable for this study. D. What scale of measurement is used for the dependent variable?

A. PARTICIPATION YES OR NO IN TAI CHI B. NOMINAL C. ARTHRITIS PAIN D. ORDENEAL/RATIO

Explain why honesty is a hypothetical construct instead of a concrete variable. Describe how honesty might be measured and defined using an operational definition.

Honesty is an internal attribute or characteristic that cannot be observed or measured directly. Honesty could be operationally defined by identifying and observing external behaviors associated with being honest, such as the physiological responses to questions measured by a polygraph ("lie detector"). Or, participants could be given a questionnaire asking how they behave or feel in situations for which honesty might have an influence.

quasi-independent variable.

In a nonexperimental study, the "independent variable" that is used to create the different groups of scores is often called the

operational definition

MEASURE AND DEFINE A HYPOTHETICAL CONSTRUCT. identifies a measurement procedure (a set of operations) for measuring an external behavior and uses the resulting measurements as a definition and a measurement of a hypothetical construct. Note that an operational definition has two components. First, it describes a set of operations for measuring a construct. Second, it defines the construct in terms of the resulting measurements.

To accomplish this goal, the experimental method has two characteristics that differentiate experiments from other types of research studies: *

Manipulation The researcher manipulates one variable by changing its value from one level to another. In the Polman et al. (2008) experiment examining the effect of violence in video games (Figure 1.5), the researchers manipulate the amount of violence by giving one group of boys a violent game to play and giving the other group a nonviolent game. A second variable is observed (measured) to determine whether the manipulation causes changes to occur. Control The researcher must exercise control over the research situation to ensure that other, extraneous variables do not influence the relationship being examined.

Environmental Variables

These are characteristics of the environment such as lighting, time of day, and weather conditions. A researcher must ensure that the individuals in treatment A are tested in the same environment as the individuals in treatment B.

Participant Variables

These are characteristics such as age, gender, and intelligence that vary from one individual to another.

In a correlational study, how many variables are measured for each individual and how many groups of individuals are in the study?

Two variables and one group

Real limits

are the boundaries of intervals for scores that are represented on a continuous number line. The real limit separating two adjacent scores is located exactly halfway between the scores. Each score has two real limits. The upper real limit is at the top of the interval, and the lower real limit is at the bottom.

variable

characteristic or condition that changes or has different values for different individuals.

Inferential statistics

consist of techniques that allow us to study samples and then make generalizations about the populations from which they were selected.

ordinal scale

consists of a set of categories that are organized in an ordered sequence. Measurements on an ordinal scale rank observations in terms of size or magnitude. GRAMMY AWARDS DONT KNOW DISTANCE (ORDERS PEOPLE) A, B, C,

nominal scale

consists of a set of categories that have different names. Measurements on a nominal scale label and categorize observations, but do not make any quantitative distinctions between observations. NAME, COLOR HAIR, RELIGION. MALE OR FEMALE, favorite reality television show,

interval scale

consists of ordered categories that are all intervals of exactly the same size. Equal differences between numbers on scale reflect equal differences in magnitude. However, the zero point on an interval scale is arbitrary and does not indicate a zero amount of the variable being measured. (YOU KNOW HOW FAR IT IS)

discrete variable

consists of separate, indivisible categories. No values can exist between two neighboring categories. (researcher studies the factors that determine # of children that couples decide to have. The variable, number of children, is ___ variable.

control condition

do not receive the experimental treatment. Instead, they either receive no treatment or they receive a neutral, placebo treatment. The purpose of a control condition is to provide a baseline for comparison with the experimental condition.

experimental condition

do receive the experimental treatment.

data set

is a collection of measurements or observations.

sample

is a set of individuals selected from a population, usually intended to represent the population in a research study.

datum (singular)

is a single measurement or observation and is commonly called a score or raw score.

parameter

is a value, usually a numerical value, that describes a population. A parameter is usually derived from measurements of the individuals in the population.

statistic

is a value, usually a numerical value, that describes a sample. A statistic is usually derived from measurements of the individuals in the sample.

ratio scale

is an interval scale with the additional feature of an absolute zero point. With a ratio scale, ratios of numbers do reflect ratios of magnitude. ABSOLUTE ZERO. WHAT IS YOU AGE__ MEAN AGE 28

Sampling error *

is the naturally occurring discrepancy, or error, that exists between a sample statistic and the corresponding population parameter.

dependent variable

is the one that is observed to assess the effect of the treatment.

population

is the set of all the individuals of interest in a particular study.

independent variable

is the variable that is manipulated by the researcher. In behavioral research, the independent variable usually consists of the two (or more) treatment conditions to which subjects are exposed. The independent variable consists of the antecedent conditions that were manipulated prior to observing the dependent variable.

The results of a recent study showed that children who routinely drank reduced fat milk (1% or skim) were more likely to be overweight or obese at age 2 and age 4 compared to children who drank whole or 2% milk (Scharf, Demmer, and DeBoer, 2013). Is this an example of an experimental or a nonexperimental study?

nonexperimental study

experimental method *

one variable is manipulated while another variable is observed and measured. To establish a cause-and-effect relationship between the two variables, an experiment attempts to control all other variables to prevent them from influencing the results.

Statistics

refers to a set of mathematical procedures for organizing, summarizing, and interpreting information.

Descriptive statistics

statistical procedures used to summarize, organize, and simplify data.

The Greek letter sigma (E) is used to stand for

summation. is read "the sum of the scores."

correlational method *

two different variables are observed to determine whether there is a relationship between them