Exam 3 Study Guide - Beginning Statistical Concepts...

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Beginning Statistical Concepts Statistics — the study of the summary, analysis, and evaluation of data. statistic – value calculated based upon information obtained from a sample that is used to estimate population information parameter – value calculated based upon information obtained from a population Levels of Measurement (types of scores) Nominal – Merely classifies objects in accordance with similarities and differences with respect to some property; no hierarchy of scores – Examples color of hair gender response to a yes/no question shoe preference Ordinal – Type of data that is rank ordered on the basis of an underlying continuum – No common unit of measurement between each score, but are ordered from high to low
– Examples class ranks place of finish in a race Interval – Data having a common unit of measurement, equal distances between score units, but having an arbitrary zero point (not a true zero) – Example temperature on Fahrenheit scale score on a knowledge test Ratio – Possesses same properties of interval data, but does have a true zero point Allows statements about equality of ratios to be made – Examples height or weight distance measurement Indicate the level of measurement for the following: Driving on U.S. Highway 280 A runner’s time of 18 min 30 sec in a road race A student 27th in a class of 157 students 44 women in a recreational golf league
The average daily temperature of 550 last March Locker number 16 A systolic blood pressure reading of 124 mm Hg A football lineman who weighs 295 lb A swimmer who finished third in a race Descriptive Statistics – Measures a trait or characteristic of a group without generalizing that statistic beyond that group. Inferential Statistics – Used to make generalizations or inferences from a smaller group (sample) to a larger group (population). – The ability to make valid inferences is a function of how representative your sample is. Central Tendency, Variability, and the Normal Curve Measures of central tendency and variability are the most commonly used and important descriptive statistics. Central Tendency
The one value that best typifies or is the most representative of all the scores in a distribution. Three measures: Mean – the arithmetic average of all the scores Median – the score that is the midpoint of the distribution Mode – the most frequently occurring score Central Tendency, Variability, and the Normal Curve Measures of Variability Indicators of the dispersion, or spread, of the scores in a distribution. – Degree of similarity among the scores. – Used with interval or ratio level data. Central Tendency, Variability, and the Normal Curve Range – the distance between the highest and lowest score in a distribution
Standard Deviation (S, or SD) – Most frequently used measure of variability. – Provides information on the average algebraic distance of each score from the mean. 3. Variance – the square of the SD, or (SD2)
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