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 distributionReference page(s): 35 What is a bimodal distribution? frequency distribution with two different values that are heavily populated with casesReference page(s): 37 Define central tendency. the most frequent, middle, or central value in a frequency distributionReference page(s): 33

 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 distributionReference page(s): 35 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 valueReference page(s): 33 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 variableReference page(s): 34 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.Reference page(s): 31 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.Reference page(s): 30 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.Reference page(s): 31

 What is a mean? the sum of the values of a variable divided by the number of valuesReference page(s): 33 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 lieReference page(s): 33 What is a mode? the category with the greatest frequency of observationsReference page(s): 33

 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 meanReference page(s): 39 What is a nominal-level variable? A measure for which different scores represent different, but not ordered, categories.Reference page(s): 30 What is an ordinal-level variable? A measure for which the scores represent ordered categories that are not necessarily equidistant from each other.Reference page(s): 30 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)Reference page(s): 37 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 meanReference page(s): 39 What is raw frequency? The total number of observations with a particular value (such as the number of respondents giving a certain response).Reference page(s): 34

 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 distributionReference page(s): 40 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).Reference page(s): 34 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.Reference page(s): 28