A sampling technique in which some units of the population have zero chance of selection or where the probability of selection cannot be accurately determined.

called accidental or opportunity sampling,

In this technique, the population is segmented into mutually exclusive subgroups and then a non-random set observations is chosen from each subgroup

This is a technique where respondents are chosen in a non-random manner based on their expertise on the phenomenon being studied.

identifying a few respondents that match the criteria for inclusion in your study, and then ask them to recommend others they know who also meet your selection criteria.

is the distortion of results due to a certain extraneous variable.

Effect on a subject receiving a fake drug or treatment. It occur when subjects believe they are getting a real drug or treatment even though they are not.

the tendency of some research subjects to describe themselves in socially approved ways.

Occurs when researchers' preferences or expectations influence the outcome of their research. In these cases, researchers see what they want to see rather than what is actually there.

To prevent Placebo Effect, one can conduct

To prevent Experimenter Bias, one can conduct

referred to as the observer effect, is a type of reactivity in which individuals improve an aspect of their behavior in response to their awareness of being observed.

the phenomenon whereby the greater the expectation placed upon people, the better they perform.

Property of "moreness"

A scale has the property of equal intervals if the difference between two points at any place on the scale has the same meaning

It is obtained when nothing of the property being measured exists

classification / categorical

rank ordering

contain equal intervals between numbers, with no absolute zero

contain equal intervals between numbers, with absolute zero

has an infinite number of possible values between any two points on the measurement scale.

can only take on a limited number of values. By their nature, all categorical variables are discrete, but so are many variables measured on ratio scales.

Measurement scales with a mathematical

The difference between the highest and the lowest

The nature and extent to which symmetry is absent

This refers to the steepness of a distribution in its center.

When is theOn the Origin of Species by Means of Natural Selection

Measure of abilities

When was the measure of abilities

When is clinical psychologist at Bellevue Hospital in New York City