# statistics ch.1

### 27 terms by will26x

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### Descriptive statistics

organize, summarize, and communicate a group of numerical observations

### Inferential statistics

use sample data to make general estimates about the larger population

### Sample

a set of observations drawn from the population of interest that, it is hoped, share the same characteristics as the population of interest

### Population

includes all possible observations about which we'd like to know something

### Variable

is any observation of a physical, attitudinal, or behavioral characteristic that can take on different values

### Construct

is a hypothetical idea that is developed (or constructed) to describe and explain human behavior

### Discrete observations

can take on only specific values (whole numbers); no other values can exist between these numbers

### Continuous observations

can take on a full range of values (numbers out to many decimal points); there is an infinite number of potential values

### Nominal variable

is a variable used for observations that have categories, or names, as their values

### Ordinal variable

is a variable used for observations that have rankings (1st, 2nd, 3rd...) as their values

### Interval variable

is a variable that has numbers as its values; the distance (or interval) between pairs of consecutive numbers is assumed to be equal

### Ratio variable

is a variable that meets the criteria for interval variables but also has a meaningful zero point

### Level

is a discrete value or condition that a variable can take on

### Independent variable

is a variable that we either manipulate or observe to determine its effects on the dependent variable

### Dependent variable

is the outcome variable that we hypothesize to be related to, or caused by, changes in the independent variable

### Confounding variable

is any variable that systematically co-varies with the independent variable so that we cannot logically determine which variable is at work; also called confound

### Extraneous variable

is a randomly distributed influence that detracts from the experimenter's efforts to measure what was intended to be measured

### Noise

influences an experiment by making the relations between variables less clear than they really are

### Reliability

refers to the consistency of a measure

### Validity

refers to the extent to which a test actually measures what it was intended to measure

### Test-retest reliability

refers to whether the scale being used provides consistent information every time the test is taken

### Predictive validity

refers to how well a measuring instrument (such as a personality scale) predicts actual behavior

### Hypothesis testing

is the process of drawing conclusions about whether a particular relation between variables is supported by the evidence

### Operational definition

specifies the operations or procedures used to measure or manipulate a variable

### Experiment

is a study in which participants are randomly assigned to a condition or level or one or more independent variables

### Random assignment

every participant is a study has an equal chance of being assigned to any of the groups, or experimental conditions, in the study

### Single-blind experiment

is one in which participants do not know the condition to which they have been assigned. This reduces the possibility that participants will respond as they believe they are expected to respond to a given situation

Example:

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