Statistics Questions & Answers

Statistics Questions & Answers Advantages of q-q plot - ANSWER: (1) The sample sizes do not need to be equal. (2) Many distributional aspects can be simultaneously tested. For example, shifts in location, shifts in scale, changes in symmetry, and the presence of outliers can all be detected from this plot. (Jk08-583) ANCOVA - ANSWER: looking at covariance and filtering out the effects of "nuisance variables" to show the relationship between the independent variable and the dependent variable. ANOVA - ANSWER: Analysis of Variance-- Arcsine Transform - ANSWER: When the data are proportions it is usually recommended that they be transformed with the arcsine transform. This takes the original data x and converts it to the transformed data y using this formula. (Jk08-28) Average Deviation - ANSWER: the mean absolute deviation that measures the absolute difference between the mean and each observation. This measure of deviation is not as well defined as is the standard deviation, partly because the mean is the least squares estimator of central tendency -so a measure of deviations that uses squared deviations is more comparable to the mean. (Jk) Bimodal Frequency Distribution - ANSWER: A combination of two normal distributions -there are two peaks. If you find that your data fall into this distribution you might consider whether the data actually represent two separate populations of measurements. (Jk08-481) causal inference - ANSWER: items or people are randomly assigned to groups such that the independent variable really is causing the difference in the dependent variable. Central Tendency - ANSWER: In statistics, a __________________ (or more commonly, a measure of ____________________) is a central value of a typical value for a probability distribution. It is occasionally called an average or just the center of the distribution. (Jk08-22)