Stats Chapter 1: Intro to Stats

Name the 4 scales of measurement

1. nominal scale 2. ordinal scale

Describe participant variables in experimental studies

age, gender, intelligence, and the like. Characteristics that vary from one individual to another and may explain differences in conclusions.

When describing data, it is necessary to distinguish whether the data come from a population or a sample. A characteristic that describes a sample is called a ________.

sample

The ratio scale

An interval scale where a value of zero corresponds to none.

Continuous variable definition

For a continuous variable, 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.

Inferential statistics definition

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

Describe a pre-post study

Quasi-experimental and nonexperimental designs consisting of a series of observations made over time. The goal is to evaluate the effect of an intervening treatment or event by comparing observations made before versus after the treatment.

Some characteristics of continuous variables

Should be very rare for identical measurements for two different people. If a substantial number of tied scores exit, suspect crude procedure or variable is not really continouous. Also each measreument is actualy an interval that must be fdefined by coundaries.

Why is a pre-post study not a true experiment?

The researcher cannot control the passage of time. Perhaps scores improved because of weather changing or other factors related to time.

Definition of statistics

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

Describe environmental variables in experimental studies

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.

What two elements are necessary for a research study to be an experiment?

What two elements are necessary for a research study to be an experiment?

A correlational study cannot demonstrate a ________-_____-______ relationship.

cause-and-effect

The relationship between variables for non-numerical data, such as gender and preferring talking or texting, is usually evaluated using a statistical technique known as a _____-_______ test.

chi-square

Whenever a research study allows more than one explanation for the results, the study is said to be ________ because it is impossible to reach an unambiguous conclusion.

confounded

Individuals in a _________ ________ 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.

control condition

A research study that simply measures two different variables for each individual is an example of the __________ method.

correlational method, or the correlational research strategy. (note each individual has two points)

Data (plural) are measurements or observations. A _____-______ is a collection of measurements or observations. A datum (singular) is a single measurement or observation and is commonly called a score or raw score.

data-set

Specific names are used for the two variables that are studied by the experimental method. The variable that is observed and measured to obtain scores within each condition is the ____________ ___________.

dependent variable

To demonstrate a cause-and-effect relationship between two variables, researchers must use the ________ method

experimental

Individuals in the _____________ ___________ do receive the experimental treatment.

experimental condition

Specific names are used for the two variables that are studied by the experimental method. The variable that is manipulated by the experimenter is called the _________ _______.

independent variable

The goal of an experimental study:

is to demonstrate a cause-and-effect relationship between two variables. Specifically, an experiment attempts to show that changing the value of one variable causes changes to occur in the second variable.

Definition of quasi-independent variable

n a quasi-experimental or nonexperimental research study, the variable that differentiates the groups or conditions being compared. Similar to the independent variable in an experiment.

The "independent variable" in a nonexperimental study is often called a _____-independent variable because it is not a true independent variable that can be manipulated.

quasi

A sample is intended to be ___________ of its population, and a sample should always be identified in terms of the population from which it was selected.

representative

In statistical terms, a set of individuals selected from a population is called a _______.

sample

There usually is some discrepancy between a sample statistic and the corresponding population parameter. This discrepancy is called _________ _______, and it creates the fundamental problem that inferential statistics must always address.

sampling error

The categories used to measure a variable make up a ________ of ___________, and the relationships between the categories determine different types of scales.

scale of measurement

This book uses the term statistics as a shortened version of ___________ ____________

statistical procedures

Key terms from this chapter

statistics population sample variable data data set datum raw score parameter statistic descriptive statistics inferential statistics sampling error correlational method experimental method independent variable dependent variable control condition experimental condition nonequivalent groups study pre-post study quasi-independent variable construct operational definition discrete variable continuous variable real limits upper real limit lower real limit nominal scale ordinal scale interval scale ratio scale

Greek letter sigma means:

summation. Add all the scores for variable x. "the sum of"

Who should always define the population for a study?

the researcher

Examples of continuous variables

time, height, weight

Note that the independent variable always consists of at least _____ values.

two (Something must have at least two different values before you can say that it is "variable.") (independent variable can be treatment vs no treatment)

Statistical techniques are classified into two general categories. What are the two categories called, and what is the general purpose for the techniques in each category?

The two categories are descriptive statistics and inferential statistics. Descriptive techniques are intended to organize, simplify, and summarize data. Inferential techniques use sample data to reach general conclusions about populations.

Variables like intelligence, anxiety, and hunger are called __________, and because they are intangible and cannot be directly observed, they are often called hypothetical __________.

constructs

The measurement obtained for each individual is called a ______ or, more commonly, a score or raw score.

datum

An English professor uses letter grades (A, B, C, D, and F) to evaluate a set of student essays. What kind of scale is being used to measure the quality of the essays?

ordinal

Why is comparing 8 year old children to 10 year old children, or people with an eating disorder to those without an eating disorder, or single parent homes to two parent homes, not a true experiment?

Because it is impossible to use techniques like random assignment to control participant variables and ensure equivalent groups, this type of research is not a true experiment.

What are constructs?

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

Descriptive statistics definition

Descriptive statistics are statistical procedures used to summarize, organize, and simplify data. Descriptive statistics are techniques that take raw scores and organize or summarize them in a form that is more manageable. Often the scores are organized in a table or a graph so that it is possible to see the entire set of scores.

The purpose of inferential statistics is to answer this question:

Does a difference between samples provide convincing evidence of a difference between the two samples, or is the difference just chance?

Definition of a population (in statistics)

A population is the set of all the individuals of INTEREST in a particular study.

Define the correlational method

A research method that simply observes two existing variables to determine the nature of their relationship.

What is "nonequivalent groups"?

A research study in which the different groups of participants are formed under circumstances that do not permit the researcher to control the assignment of individuals to groups and the groups of participants are, therefore, considered nonequivalent. (think males, females--pre-existing groups)

Definition of statistic

A 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.

Define "variable"

A variable is a characteristic or condition that changes or has different values for different individuals (height, weight, personality, etc).

A survey asks people to identify their age, annual income, and marital status (single, married, divorced, etc.). For each of these three variables, identify the scale of measurement that probably is used and identify whether the variable is continuous or discrete.

Age and annual income are measured on ratio scales and are both continuous variables. Marital status is measured on a nominal scale and is a discrete variable

What is an "operational definition"?

An operational definition 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.

The interval scale

An ordinal scale where all the categories are intervals with exactly the same width.

Order of mathematical operations

1. Any calculation contained within parentheses is done first. 2. Squaring (or raising to other exponents) is done second. 3. Multiplying and/or dividing is done third. A series of multiplication and/or division operations should be done in order from left to right. 4. Summation using the Σ notation is done next. 5. Finally, any other addition and/or subtraction is done.

The experimental method has two characteristics that differentiate experiments from other types of research studies:

1. Manipulation 2. Control

There are two general categories of variables that researchers must consider in an experimental study:

1. Participant variables 2. Environmental variables

Researchers typically use three basic techniques to control other variables:

1. Random assignment (random) 2. Matching (all groups 60% female, 40% male) 3. Holding variables constant (all female, all 10 years old)

Specifically, statistics serve two general purposes:

1. Statistics are used to organize and summarize the information so that the researcher can see what happened in the research study and can communicate the results to others. 2. Statistics help the researcher to answer the questions that initiated the research by determining exactly what general conclusions are justified based on the specific results that were obtained.

The problem for inferential statistics is to differentiate between the following two interpretations:

1. There is no real difference between the two methods, and the 5 difference between the samples is just an example of sampling error (like the samples in Figure 1.2). 2. There really is a difference between the two methods, and the difference between the samples was caused by the different methods.

Discrete variable definition

A discrete variable consists of separate, indivisible categories. No values can exist between two neighboring categories. Whole, countable numbers.

The ordinal scale

A measurement scale consisting of a series of ordered categories. Think first, second, third, etc. You can see that groups are different and determine direction of difference, but you can not tell size of the difference. (perhaps Timmy is a better reader, but you don't know by "how much")

The nominal scale

A measurement scale where the categories are differentiated only by qualitative names. Important to note that you can say two things are different, but you can not identity direction or the size of the difference.

Definition of parameter

A 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.

What are "real limits" when describing continuous variables?

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.

Researchers have observed that high school students who watched educational television programs as young children tend to have higher grades than their peers who did not watch educational television. Is this study an example of an experiment? Explain why or why not.

Researchers have observed that high school students who watched educational television programs as young children tend to have higher grades than their peers who did not watch educational television. Is this study an example of an experiment? Explain why or why not.

Definition of sampling error

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

A researcher is interested in the texting habits of high school students in the United States. If the researcher measures the number of text messages that each individual sends each day and calculates the average number for the entire group of high school students, the average number would be an example of a ___________.

parameter

When describing data, it is necessary to distinguish whether the data come from a population or a sample. A characteristic that describes a population—for example, the average score for the population—is called a ___________.

parameter