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QMB3250 EXAM with correct answers
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QMB3250 EXAM with correct answers
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QMB3250 EXAM with correct answerssimple moving average - ANSWER: ➡ forecast is the average of a fixed number of past periods
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simple exponential smoothing - ANSWER: ➡ allows you to adjust the weight between recent
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and historic data; forecast t + 1
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autoregressive methods - ANSWER: ➡ good for quarterly trends and seasonal*, uses lag o o o oo o o o o o o o o
variables (start from bottom to top/last to first)
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y hat = b0 + b1ylag1 + b2ylag2 + etc.
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(# means time period back)
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- JMP: fit model, add: lags, run
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random walks - ANSWER: ➡ previous point is our best guess of the next point
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- assumptions: quantitative data, measured on negative intervals
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multiple regression models (2 types) - ANSWER: ➡ better at predicting more than just the
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next point & seasonal components (uses indicator variables)
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- linear (additive)
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- exponential (multiplicative, uses log(y), consistent % increase)
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additive model slope interpretation - ANSWER: ➡ b is the increase in y for a one-unit change in
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x (consistent increase)
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interpreting the slope of log/multiplicative model - ANSWER: ➡ log10(y)--> multiplying y by
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10^slope
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=> % of consistent increase/decrease in y, incr/decr shown by if there is a 1.05 or just 0.05
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, one way ANOVA - ANSWER: ➡ to compare 2 or more means
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H0: mu1 = mu2 = ... = mu k (no diff in treatments)
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Ha: at least one population mean is diff from the rest
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assumptions: indepence/random, equal variance, normal populationo o o o o
one way ANOVA assumptions - ANSWER: ➡ independence- randomizaiton
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equal variance- resid vs. predicted plot
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normal population- outliers of boxplots, histogram bell-shaped, normal quantile plot
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Bonferroni- finding # of comparisons - ANSWER: ➡ a (a-1)/2 o o o o o o oo o o
--> a = #levels
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Bonferroni- individual error rate - ANSWER: ➡ family wise error rate / # comparisons
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Bonferroni- Family wise confidence level - ANSWER: ➡ 1 - (alpha / individual error rate)
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Tukey's method - ANSWER: ➡ done after ANOVA
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estimates the difference in population means o o o o o
two way ANOVA - ANSWER: ➡ 2 factors with multiple levels
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H0: pop mean error is same at all levels for the factor- interaction is NOT signif- look at main
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effects
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Ha: at least one pop mean errors is diff- interaction is signif- multiple comparisonsTukey
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Wilcoxon Rank Sum test - ANSWER: ➡ nonparametric test that compares sample medians of
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two independent groups of scores
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H0: two samples come from the same distribution
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