WGU C955 Probability and Statistics Exam Questions & Answers Correct 100%

Boxplot - Answer an image that has min, Q1, median, Q3, max Histogram - Answer A graphical representation -- bars, measuring the frequency within each interval Skewed right - Answer Not a symmetric distribution, the tail is on the right, i.e. extra stuff on the right Measures of center - Answer Median, the mean (and mode) Measures of spread - Answer Range, IQR & standard deviation Standard Deviation Rule - Answer 68% of the data are within 1 standard deviation, 95% are within 2, 99.7 are within 3 standard deviations from the mean. For skewed data, use these for center and spread - Answer In this situation, we use median (for center) & IQR (for spread) Explanatory variable - Answer In a study, what we think is the "cause" Response variable - Answer In a study, what we think is the "effect" Scatter plot - Answer A graphical representation of Q -> Q Two way table - Answer A graphical representation of C -> C Side-by side box - Answer A graphical representation of C -> Q Linear relationship - Answer "shaped like a line" Correlation coefficient, r - Answer Between -1 and 1; measures how close the points are to the line and if the trend is uphill (positive) or downhill (negative). r = -0.2, for example - Answer This is an example of a correlation coefficient that represents a weak negative correlation. r = 0.9, for example - Answer This is an example of a correlation coefficient that represents a strong positive correlation. Linear regression line - Answer A line that fits the data as close as possible, used to make predictions Interpolation - Answer Making predictions *within* the range of your data. This is usually accurate. Extrapolation - Answer Making predictions *outside* of the range of your data. This is generally a bad idea. Simpson's Paradox - Answer When split up, each data set can have a pattern which goes away when all the data is combined. Only way to prove causation - Answer Experiments, because they account for lurking variables Observational study - Answer A type of study where we measure or survey members of a sample without trying to affect them. Cannot prove causation. Experimental study - Answer A study where you split subjects up randomly and impose a change on one group to study the effect; can prove causation Prospective study - Answer Is a study that's done over time to find results / A study watching for outcomes during the study period