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1) Sample variance divides by n − 1 (degrees of freedom).
2) The population standard deviation in Excel is STDEV.S.
3) The median is strongly affected by extreme outliers.
4) For even n, the median is the mean of the two middle values (after sorting).
5) The range (max − min) is robust to outliers.
6) The interquartile range equals Q3 − Q1.
7) A standard deviation can never be negative.
8) If all values are identical, both variance and standard deviation are 0.
9) Adding a constant c to every observation increases the mean by c and leaves the standard deviation unchanged.
10) Multiplying all observations by 2 multiplies the variance by 2.
11) A stem‑and‑leaf plot discards the original data values and only keeps grouped counts.
12) With leaf unit 1, the number 137 is shown as 1| 37.
13) Leaves within each stem should be shown in sorted order for readability.
14) Splitting stems into 0–4 and 5–9 rows can reveal shape more clearly.
15) Histograms are typically not used for quantitative (numerical) variables, but for categorical ones.
16) If histogram bins have unequal widths, comparing bar heights alone can be misleading.
17) With equal‑width bins, each bar’s area (and height) is proportional to the count in that bin.
18) The x‑axis of a histogram shows every individual data point in sorted order.
19) Choosing too few bins can hide structure; too many bins can show noise.