Organization of Terms
Central Limit Theorem
Glossary of Terms
Statistics - a set of concepts, rules, and procedures that help us to: organize numerical information in the form of tables, graphs, and charts; understand statistical techniques underlying decisions that affect our lives and well-being; and make informed decisions.
Data - facts, observations, and information that come from investigations. Measurement data sometimes called quantitative data -- the result of using some instrument to measure something (e.g., test score, weight); Categorical data also referred to as frequency or qualitative data. Things are grouped according to some common property(ies) and the number of members of the group are recorded (e.g., males/females, vehicle type).
Variable - property of an object or event that can take on different values. For example, college major is a variable that takes on values like mathematics, computer science, English, psychology, etc. Discrete Variable - a variable with a limited number of values (e.g., gender (male/female), college class (freshman/sophomore/junior/senior). Continuous Variable - a variable that can take on many different values, in theory, any value between the lowest and highest points on the measurement scale. Independent Variable - a variable that is manipulated, measured, or selected by the researcher as an antecedent condition to an observed behavior. In a hypothesized cause-and-effect relationship, the independent variable is the cause and the dependent variable is the outcome or effect. Dependent Variable - a variable that is not under the experimenter's control -- the data. It is the variable that is observed and measured in response to the independent variable. Qualitative Variable - a variable based on categorical data. Quantitative Variable - a variable based on quantitative data. Graphs - visual display of data used to present frequency distributions so that the shape of the distribution can easily be seen. Bar graph - a form of graph that uses bars separated by an arbitrary amount of space to represent how often elements within a category occur. The higher the bar, the higher the frequency of occurrence. The underlying measurement scale is discrete (nominal or ordinal-scale data), not continuous. Histogram - a form of a bar graph used with interval or ratio-scaled data. Unlike the bar graph, bars in a histogram touch with the width of the bars defined by the upper and lower limits of the interval. The measurement scale is continuous, so the lower limit of any one interval is also the upper limit of the previous interval. Boxplot - a graphical representation of dispersions and extreme scores. Represented in this graphic are minimum, maximum, and quartile scores in the form of a box with "whiskers." The box includes the range of scores falling into the middle 50% of the distribution (Inter Quartile Range = 75th percentile - 25th percentile)and the whiskers are lines extended to the minimum and maximum scores in the distribution or to mathematically defined (+/-1.5*IQR) upper and lower fences. Scatterplot - a form of graph that presents information from a bivariate distribution. In a scatterplot, each subject in an experimental study is represented by a single point in two-dimensional space. The underlying scale of measurement for both variables is continuous (measurement data). This is...
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