Psych 3402 - Statistics Exam 1 Study Guide

values that organize and describe the characteristics of a collection of data sometimes called a data set. - descriptive statistics tools that are used to make infer characteristics of a population, based on data from that population. - inferential statistics a subset of the population - sample all the possible subjects or cases of interests - population A method of investigation used to demonstrate cause-and-effect relationships by purposely manipulating variable(s) thought to produce change in another factor. - experimental method the experimental factor that is manipulated - independent variable The measurable effect for all groups. - dependent variable what we are looking at something we want to research (a concept, how I think of a tree versus how you see a tree in your mind). - constructs mean, median, mode - measures of central tendency the average of the scores expressed with the capital letter M. - mean the middle score in a distribution; half the scores are above it and half are below it (50th percentile). - median the most frequently occurring score(s) in a distribution - mode extraneous factor that interferes with the action of the independent variable on the dependent variable - confounding variable variable that has specific values and that cannot have values between these specific values. Example: number of siblings, # of people killed this year from drunk driving accidents. - discrete variable a quantitative variable that has an infinite number of possible values that are not countable. Example: height, age, profits earned by a certain company. - continuous variable describes a categorical group discrete variable fixed, cannot be changed Example: sex, political affiliation sorted by name - what is a nominal scale of measurement? describes a group by hierarchy but gives no distance between items. Discrete variables Example: marathon race - what is an ordinal scale of measurement? describes a thing with specific ranges and distances between each point. zero is just another point on the scale Continuous variables. - What is an interval scale of measurement? continuous variables fixed points of measurement has an absolute zero no negative - What is a ratio scale measurement? computed by multiplying the value by the frequency of its occurrence, adding all it's products, and then dividing by the total number of occurrences. - weighted mean range, variance, standard deviation - measures of variability standard deviation squared ss/df = sum of squares/degrees of freedom - does not measure units - how much a score deviates from the mean. * Σ (X- MEAN) = 0 (WILL ALWAYS EQUAL ZERO) - Variance equals zero = no change - variance the corrected variance - returns the same unit of measurement as the original score - uses the square function to return a value above or below the mean ignoring the direction. - standard deviation inflates the variance (and standard deviation) to account for missing information in the sample. - degrees of freedom the difference between the highest and lowest scores in a distribution. two types (exclusive, inclusive) - range highest score - lowest score - exclusive range highest score - lowest score + 1 (counts the starting point) - inclusive range