Newly Released WGU Applied-Probability-and-Statistics Exam PDF

Expected value is the long-run average value of a random variable. For a discrete random variable, it is calculated by multiplying each possible value by its probability and then adding those products. Here, the expression is already structured as an expected value calculation: 1×0.2 + 2×0.5 + 3×0.3. Compute each product: 1×0.2 = 0.2, 2×0.5 = 1.0, and 3×0.3 = 0.9. Add them: 0.2 + 1.0 + 0.9 = 2.1. Therefore, the expected value is 2.1. This does not mean the random variable must equal 2.1 in a single trial; it means that over many repetitions, the average outcome would approach 2.1. Option B is close but omits part of the weighted contribution. Options C and D do not match the weighted-average computation. Study Guide references/topics: expected value, discrete random variables, weighted average, probability distributions.

============

This experiment has two independent stages: tossing a coin and spinning a numbered spinner. The probability of getting heads on a fair coin is 1/2. The spinner has 8 equally likely outcomes numbered 1 through 8. A number less than 3 means either 1 or 2, so there are 2 favorable spinner outcomes out of 8 total outcomes. Thus, P(number less than 3) = 2/8 = 1/4. Since the coin result does not affect the spinner result, the events are independent. For independent events connected by “and,” multiply the probabilities: 1/2 × 1/4 = 1/8. Equivalently, the combined sample space has 2 coin outcomes times 8 spinner outcomes, or 16 total equally likely outcomes. The favorable outcomes are heads with 1 and heads with 2, giving 2/16 = 1/8. References/topics from the Study Guide: independent events, sample spaces, multiplication rule, theoretical probability.

A histogram is used to display the frequency distribution of quantitative numerical data, especially continuous data grouped into intervals or bins. For example, a histogram can show the distribution of heights, test scores, commute times, or weights. Each bar represents a numerical interval, and the height of the bar represents how many observations fall within that interval. Unlike a bar chart, the bars in a histogram usually touch because the intervals form a continuous numerical scale. Option B is incorrect because categorical data are better displayed with a bar chart or pie chart. Option C is incorrect because a scatterplot displays the relationship between two quantitative variables, not the frequency distribution of one variable. Option D is incorrect because a boxplot summarizes median, quartiles, spread, and outliers rather than showing detailed frequency counts. The correct graph for continuous numerical frequency is a histogram. Study Guide references/topics: histograms, quantitative data, frequency distributions, graphical displays.

============

Simpson’s paradox occurs when an association observed in aggregated data reverses or conflicts with the association observed within relevant subgroups. In this case, the overall recovery rate appears better for Treatment Y, since Y has a 90% overall recovery rate compared with 80% for Treatment X. However, after the data are divided by age group, Treatment X has a higher recovery rate in every age group. That reversal between the overall comparison and the subgroup comparisons is precisely the defining structure of Simpson’s paradox. Age group functions as the lurking or confounding variable because different age distributions across treatment groups can distort the overall recovery rates. Option B states a true overall fact, but it ignores the contradiction created by the age-specific rates. Option C is too general; simple differences between treatments do not necessarily create Simpson’s paradox. The key issue is inconsistency between aggregate and stratified results. References/topics from the Study Guide: two-variable data, confounding variables, conditional comparisons, Simpson’s paradox.

============