What is an alternative hypothesis? a statement about the value or values of a population parameter. A hypothesis proposed as an alternative to the null hypothesis What is a bar chart? A graphic display of the data in a frequency or percentage distribution. What is a bimodal distribution? frequency distribution with two different values that are heavily populated with cases Define central tendency. the most frequent, middle, or central value in a frequency distribution

 What is a confidence interval? the range of values into which a population parameter is likely to fall for a given level of confidence What is a confidence level? the degree of belief or probability that an estimated range of values includes or covers the population parameter What is a cumulative proportion/percentage? the total proportion of observations at or below a value in a frequency distribution What is a data matrix? an array of rows and columns that stores the values of a set of variables for all the cases in a data set

 What is a descriptive statistic? the mathematical summary of measurements for one variable What is deviation? The deviation of an observation from the sample mean is the difference between them. What is dispersion? the distribution of data values around the most frequent, middle, or central value What is the empirical rule? If the histogram of the data is approximately bell shaped, then (1) about 68% of observations fall within one standard deviation of the mean, (2) about 95% of observations fall within two standard deviations of the mean, and (3) nearly all of observations fall within three standard deviations of the mean.

 What is a frequency distribution (f)? the number of observations per value or category of a variable What is a histogram? a type of bar graph in which the height and area of the bars are proportional to the frequencies in each category of a nominal variable or intervals of a continuous variable What is an index? A multi-item measure in which individual scores on a set of items are combined to form a summary measure. What is an index of diversity? a measure of variation for categorical data that can be interpreted as the probability that two individuals selected at random would be in different categories

 What is an index of qualitative variation? a measure of variation for categorical data that is the index of diversity adjusted by a correction factor based on the number of categories of the variable What is an interquartile range? the middle 50 percent of observations What is an interval-level variable? A measure for which a one-unit difference in scores is the same throughout the range of the measure. What is a Likert Scale? A multi-item measure in which the items are selected based on their ability to discriminate between those scoring high and those scoring low on the measure.

 What is a mean? the sum of the values of a variable divided by the number of values What is mean absolute deviation? a measure of dispersion of data points for interval- and ratio-level data What is a median? the category or value above and below which one-half of the observations lie What is a mode? the category with the greatest frequency of observations

 What is negative skew? a distribution of values in which fewer observations lie to the left of the middle value and those observations are fairly distant from the mean What is a nominal-level variable? A measure for which different scores represent different, but not ordered, categories. What is an ordinal-level variable? A measure for which the scores represent ordered categories that are not necessarily equidistant from each other. What is an outlier? An observation is an outlier if it fails more than 1.5(IQR) above the upper quartile or more than 1.5(IQR) below the lower quartile (IQR = interquartile range).

 What is a percentile rank? reports the percentage of cases in a distribution that lie below it (ex: 97th percentile on the SAT) What is a pie diagram? a circular graphic display of a frequency distribution What is positive skew? a distribution of values in which fewer observations lie to the right of the middle value and those observations are fairly distant from the mean What is raw frequency? The total number of observations with a particular value (such as the number of respondents giving a certain response).

 What is relative frequency? percentage or proportion of total number of observations in a frequency distribution that have a particular value What is relative frequency? The relative frequency for a category is the proportion or percentage of the observations that fall in that category. What is a resistant measure of central tendency? a measure of dispersion of central tendency that is not sensitive to one or a few extreme values in a distribution What is the standard normal distribution? normal distribution with a mean of 0 and a standard deviation and variance of 1

 What is statistical significance? the probability of making a type I error What is a total frequency? The sum of raw frequencies (usually presented in a table). What is a trimmed mean? the mean of a set of numbers from which some percentage of the largest and smallest values has been dropped What is a variable? A characteristic that can vary in value among subjects in a sample or population.

 What is intercoder reliability? demonstration that multiple analysts, following the same content analysis procedure, agree and obtain the same measurements What is an additive index? Summation of ordinal variables, each of which is coded identically, and all of which are measures of the same concept. Also called a summative scale or ordinal scale. What is automated content analysis? Content analysis, which entails transforming non-numeric text into numeric data, done through automated programs or algorithms. What is centrality (in a network)? In regards to social networks, is the importance of nodes in the network based on their connections – nodes with more connections are viewed as being more central.

 What is a density plot? Alternative to histograms, display a “running average” of observations across the range of observed values. Also called kernel density plots. What is mean centering? Process that involves subtracting the mean value of the variable from each observed value. What is network analysis? Process of transforming evidence of social connections among people into quantitative measures and maps of social structures that explain political phenomena or other social phenomena. Define range (of a variable). Measure of variability of data, determined by subtracting the minimum value from the maximum value.

 What is skewness? Measure of symmetry of data, relates to variability – the more skewed a data set is, the less symmetrical it is. What is standard deviation? Measure of variability, summarizes the extent to which the cases in an interval-level distribution fall on or close to the mean of the distribution. It is the square root of the variance. What is standardizing? Process of relating scores to the mean using the standard deviation – dividing the difference from the mean by the standard deviation of scores yields standardized scores that are independent of characteristics of the assessment. What is variance? A summary of the dispersion of an interval-level variable. The sum of squared deviations divided by n-1. The square root of which is the standard deviation.