The question asks for the total number of students who scored at least 80 on the quiz. From the histogram, I need to identify the bins for scores 80-89 and 90-99, then add their frequencies. The 80-89 bin shows 8 students and the 90-99 bin shows 6 students. Adding these together: 8 + 6 = 14 students scored at least 80. A common mistake is including the 70-79 bin or only counting one of the two relevant bins, so carefully identify which score ranges meet the "at least 80" criterion.

The question asks how many more checkouts occurred from 2–4 than from 10–12 based on the histogram. The bar for 2–4 reaches 40 checkouts, and for 10–12 it reaches 20 checkouts, as indicated by the y-axis. Subtract the values: 40 - 20 = 20 checkouts. Errors often arise from confusing adjacent bars or misreading the scale, leading to differences like 15 or 25. Double-check bar heights against the axis and ensure you're comparing the correct time blocks.

The question asks how many students scored between 30 and 39 inclusive on the quiz, based on the histogram. In the histogram, the bar for the 30–39 interval reaches 8 on the y-axis, indicating the frequency. Thus, 8 students fall into this bin. Remember, histograms display counts in intervals, so read the height directly for that specific bin. A key error is misreading the bin labels or confusing height with cumulative totals; always align with the x-axis intervals carefully.