Stats Essay

666 WordsSep 15, 20143 Pages
AP Statistics study guide @Sunday, 1-9-14@9:33AM Chapter 2 * Density functions * Find the percentage of values falling between values on a density curve: normalcdf(min, max, mean, SD) * Interpretation of z scores: * A z score less than 0 represents an element less than the mean. * A z score greater than 0 represents an element greater than the mean. * A z score equal to 0 represents an element equal to the mean. * A z score equal to 1 represents an element that is 1 standard deviation greater than the mean, etc. * A z score equal to -1 represents an element that is 1 standard deviation less than the mean, etc. * Normal Distribution problems: * Given mu and sigma find probability greater than, less than, or between: normalcdf(x, 1E99, mu, sigma), normalcdf(-1E99, x, mu, sigma), normalcdf(x, y, mu, sigma * Relationships between z scores, percentiles, and quartiles: Q1 corresponds to P25, Q3 represents to P75, and Q2 is the median. Chapter 5: * Experiments vs. observational studies: * Observational: A study based on data in which no manipulation of factors has been employed * Experimental: Manipulates factor levels to create treatments, randomly assigns subjects to these treatment levels, then compares the responses of the subject groups across treatment levels * Sampling strategies and bias: * Types of biases: * Undercoverage- occurs when some members of the population inadequately represented in the sample. * Nonresponse- When an individual doesn’t participate in the survey * Voluntary- When sample members are self selected volunteers * Types of sampling: * Stratified- Population is divided into groups, based on some characteristic. Then within a group a probability sample is selected. Groups are called strata * Cluster- Every member of the population is assigned to one and