Single Group Threats
« PreviousHomeNext » The Single Group Case What is meant by a "single group" threat? Let's consider two single group designs and then consider the threats that are most relevant with respect to internal validity.
Market Research Software Provides Correlation for Quantifiable Data
Correlation is a statistical technique that can show whether and how strongly pairs of variables are related. For example, height and weight are related; taller people tend to be heavier than shorter people. The relationship isn't perfect. People of the same height vary in weight, and you can easily think of two people you know where the shorter one is heavier than the taller one. Nonetheless, the average weight of people 5'5'' is less than the average weight of people 5'6'', and their average weight is less than that of people 5'7'', etc. Correlation can tell you just how much of the variation in peoples' weights is related to their heights.

Types of Validity
« PreviousHomeNext » There's an awful lot of confusion in the methodological literature that stems from the wide variety of labels that are used to describe the validity of measures. I want to make two cases here. First, it's dumb to limit our scope only to the validity of measures. We really want to talk about the validity of any operationalization. That is, any time you translate a concept or construct into a functioning and operating reality (the operationalization), you need to be concerned about how well you did the translation.
DMP - Stem and Leaf Displays
Stem and Leaf Displays Author(s) David M. Lane Prerequisites Distributions
Correlation does not imply causation
Assessment | Biopsychology | Comparative | Cognitive | Developmental | Language | Individual differences | Personality | Philosophy | Social |Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology | Statistics:Scientific method · Research methods · Experimental design · Undergraduate statistics courses · Statistical tests · Game theory · Decision theory "Correlation does not imply causation" (related to "ignoring a common cause" and questionable cause) is a phrase used in science and statistics to emphasize that a correlation between two variables does not automatically imply that one causes the other (though correlation is necessary for linear causation in the absence of any third and countervailing causative variable, it can indicate possible causes or areas for further investigation; in other words, correlation is a hint).[1][2]

Voice Capture Software by The Survey System
Standard capture of comments and similar answers require a painstaking manual transcription process that is subject to errors and misinterpretations. For example, did your respondent say in response to a question about a TV news announcer ... THAT’s an anchor man!!! Or did he say ...
G*Power 3
G*Power is a tool to compute statistical power analyses for many different t tests, F tests, χ2 tests, z tests and some exact tests. G*Power can also be used to compute effect sizes and to display graphically the results of power analyses. Whenever we find a problem with G*Power we provide an update as quickly as we can. We will inform you about updates if you

DMP - When to Use Mean, Median, or Mode
Introduction A measure of central tendency is a single value that attempts to describe a set of data by identifying the central position within that set of data. As such, measures of central tendency are sometimes called measures of central location.
We Check Out the Numbers Behind the News
Causation vs. Correlation One of the most common errors we find in the press is the confusion between correlation and causation in scientific and health-related studies. In theory, these are easy to distinguish — an action or occurrence can cause another (such as smoking causes lung cancer), or it can correlate with another (such as smoking is correlated with alcoholism). If one action causes another, then they are most certainly correlated. But just because two things occur together does not mean that one caused the other, even if it seems to make sense.

Statistical Significance By The Survey System
"Significance level" is a misleading term that many researchers do not fully understand. This article may help you understand the concept of statistical significance and the meaning of the numbers produced by The Survey System. This article is presented in two parts. The first part simplifies the concept of statistical significance as much as possible; so that non-technical readers can use the concept to help make decisions based on their data. The second part provides more technical readers with a fuller discussion of the exact meaning of statistical significance numbers.

Regular Expressions as used in R
Description This help page documents the regular expression patterns supported by grep and related functions grepl, regexpr, gregexpr, sub and gsub, as well as by strsplit. Details A ‘regular expression’ is a pattern that describes a set of strings.
G*Power Data Analysis Examples: Power analysis for two-group independent sample t-test
G*Power Data Analysis Examples Power analysis for two-group independent sample t-test NOTE: This page was developed using G*Power version 3.0.10. You can download the current version of G*Power from . You can also find help files, the manual and the user guide on this website. Examples

DMP - Collecting and Analyzing Data
What do we mean by collecting data?What do we mean by analyzing data?Why should you collect and analyze data for your evaluation?
Identifying Psychological Variables
Benjamin D. Wright & Shirley A. Tuska, The School Review, Vol. 76, No. 3, September 1968

Sample Size Calculator The Sample Size Calculator is a free on-line resource, which indicates what sample size you would need in order to be confident in your results: www.surveysystem.com/sscalc.htm by raviii Mar 3