QMB 3200 Exam 3 |Complete Questions with 100% Correct Answers

QMB 3200 Exam 3 |Complete Questions with 100% Correct Answers The variable selection procedure that identifies the best regression equation, given a specified number of independent variables, is: best-subsets regression. The mathematical equation that explains how the dependent variable y is related to several independent variables and has the form is called: a multiple regression model. A regression model between sales ( in $1,000) and unit price (x1 in dollars) and television advertisement (x2 in dollars) resulted in the following function: . The coefficient of the unit price indicates that if the unit price is: increased by $1 (holding advertisement constant), the sales are expected to decrease by $3,000. If a categorical variable has k levels, then: k - 1 dummy variables are needed. When constructing a confidence or a prediction interval to quantify the relationship between two quantitative variables, the appropriate degrees of freedom are: n-2 Influential observations always: None of the above are correct. They can increase or decrease the value of the slope, correlation, and y-intercept depending on where they fall in relation to the rest of the points in the data set. The model developed from sample data that has the form is known as the: estimated regression equation. When autocorrelation is present, which of the following assumptions is violated? The error terms are independent. high leverage points The mathematical equation relating the independent variable to the expected value of the dependent variable, , is known as the: Dummy variables must always have: When we conduct significance tests for a multiple regression relationship, the F test will be used as the test for: overall significance. When carrying out an F test to determine if the addition of extra predictor variables results in a significant reduction in the error sum of squares, what are the degrees of freedom of the numerator and denominator of the F statistic? The numerator degrees of freedom equals the number of predictors added to the model. The denominator degrees of freedom is n—p—1. How many independent variables does the forward selection process start with? Zero In best-subsets regression, Minitab can be used to provide output that identifies the two best one-variable estimated regression equations, the two best two-variable estimated regression equations, the two best three-variable estimated regression equations, and so on. What criterion is used in determining which estimated regression equations are best? R^2 In order to use the output from a multiple regression model to perform the ANOVA test on the difference among the means of four populations, how many dummy variables do we need to use to indicate treatments? Three The effect of two independent variables acting together is called: interaction. The tests of significance in regression analysis are based on assumptions about the error term ɛ. One such assumption is that the error term follows ɛ a(n) _____ distribution for all values of x. normal In multiple regression analysis, the general linear model: can be used to accommodate curvilinear relationships between the independent variables and the dependent variable. An observation that has a strong influence or effect on the regression results is called a(n): influential observation. In a regression analysis, an outlier will always increase: the value of the correlation. In multiple regression analysis: there can be several independent variables, but only one dependent variable. The value of the coefficient of correlation (r): can be equal to the value of the coefficient of determination (r^2). In a multiple regression model, the values of the error term, ε, are assumed to be: independent of each other. The Durbin-Watson test is generally inconclusive for: smaller sample sizes. If a residual plot of x versus the residuals, y - ŷ, shows a non-linear pattern, then we should conclude that: the regression model is not an adequate representation of the relationship between the variables. A variable used to model the effect of categorical independent variables is called a(n): dummy variable. In a multiple regression model, the error term ε is assumed to have a mean of: 0. In general, R^2 always _____ as independent variables are added to the regression model. increases If the coefficient of determination is a positive value, then the coefficient of correlation: can be either negative or positive. The tests of significance in regression analysis are based on several assumptions about the error term ɛ. Additionally, we make an assumption about the form of the relationship between x and y. We assume that the relationship between x and y is: linear. In a multiple regression model, the variance of the error term, ε, is assumed to be: the same for all values of x1, x2,..., xp. An F test, based on the F probability distribution, can be used to test for: significance in regression. All things held constant, which interval will be wider: a confidence interval or a prediction interval? Prediction interval In a multiple regression model, the values of the error term, ε, are assumed to be: normally distributed. A graph of the standardized residuals plotted against values of the normal scores that helps to determine whether the assumption that the error term has a normal probability distribution appears to be valid is called a: