In AP Statistics, the range is a measure of variability equal to the maximum data value minus the minimum data value. It is a single number, not an interval, and it is nonresistant because one extreme outlier can change it dramatically.
The range is the simplest measure of spread you'll use in AP Stats. Take the biggest value in the dataset, subtract the smallest value, and you're done. If room sizes in a dorm run from 100 to 300 square feet, the range is 200 square feet. One number, summarizing how far apart the extremes sit.
That simplicity is also its weakness. Because the range depends on exactly two data points (the max and the min), it ignores everything in between and gets yanked around by outliers. The CED calls measures like this nonresistant (or non-robust). The range sits alongside the interquartile range and standard deviation as the three measures of variability named in Topic 1.7, and on the exam you're expected to know when each one is the right tool.
Range lives in Unit 1: Exploring One-Variable Data, specifically Topic 1.7 (Summary Statistics for a Quantitative Variable). It directly supports learning objective 1.7.B (calculate measures of variability) and, more importantly, 1.7.C (explain why you'd pick one measure over another). That second objective is where the points actually are. The CED explicitly labels the range as nonresistant, grouping it with the mean and standard deviation, while the median and IQR are resistant. Any time a question gives you a skewed distribution or a dataset with outliers and asks which summary statistics to trust, the range is part of that conversation. It also shows up whenever you describe a distribution under objective 1.6.A, since every full description needs shape, center, and variability, and range is the fastest variability number you can report.
Keep studying AP Statistics Unit 1
Interquartile Range (IQR) (Unit 1)
IQR is the range's resistant cousin. Instead of max minus min, it's Q3 minus Q1, so it measures the spread of the middle 50% and shrugs off outliers. Two datasets can share the same range of 50 while one has an IQR of 15 and the other an IQR of 8, which tells you the second dataset is more tightly clustered in the middle even though its extremes are just as far apart.
Standard Deviation (Unit 1)
Standard deviation is the third measure of variability in Topic 1.7, and like the range it's nonresistant. The difference is that standard deviation uses every data value, measuring typical distance from the mean, while the range uses only two values. A quick gut check: the range puts a ceiling on how spread out data can be, so standard deviation is always smaller than the range.
Outliers and Skewness (Unit 1)
Describing a distribution under objective 1.6.A means flagging unusual features like outliers and skew. A single extreme value barely moves the median or IQR but can inflate the range enormously. That's exactly why a five-number summary with Max = 89 and Q3 = 31 should make you suspicious: the range is being driven by one weird point.
Sampling Variability (Unit 3)
Range describes spread within one dataset, but the bigger idea of variation carries through the whole course. When you later study how statistics vary from sample to sample, you'll keep using spread comparisons. The habit of saying 'this group's values are more spread out than that group's' starts here with the range.
Range is rarely the star of a question, but it's everywhere in supporting roles. Multiple-choice questions love handing you a five-number summary with a suspicious max (like Min = 12, Q1 = 15, Median = 22, Q3 = 31, Max = 89) and asking which statistic the maximum affects most. The answer is the range, since it's built directly from the max. Another classic stem gives two datasets with the same range but different IQRs and asks you to compare their spreads. On FRQs, range earns points when you compare distributions. The 2019 FRQ Q1 gave a histogram of room sizes and asked for a description, and any complete description includes variability; range is a legitimate way to address it. The 2017 FRQs on clay chemistry and schizophrenia diagnosis ages similarly required comparing variability between groups. Two rules for free-response writing: always include units (a range of '200 square feet,' not just '200'), and report the range as a single number, never as 'from 12 to 89.'
Both measure variability with a subtraction, but they subtract different things. Range = Max − Min and uses the two most extreme points, so it's nonresistant. IQR = Q3 − Q1 and uses the quartiles, so outliers can't touch it. When a distribution is skewed or has outliers, report median and IQR; the range can still appear as extra description, but the IQR is the measure the exam wants you to lean on. Don't write 'IQR' when a question asks for the range, and don't use 1.5 × range in the outlier rule (it's 1.5 × IQR).
The range equals the maximum value minus the minimum value, and it is reported as one single number, not as an interval like '12 to 89.'
Range is nonresistant, meaning a single outlier can inflate it dramatically, which puts it in the same camp as the mean and standard deviation.
The median and IQR are the resistant alternatives, so when data are skewed or have outliers, the IQR is the better measure of spread to lean on.
Two datasets can have identical ranges but very different IQRs, which means the range alone tells you nothing about how the middle of the data is spread.
On FRQs, mentioning the range with correct units is a quick, valid way to address variability when describing or comparing distributions.
The outlier fence rule uses 1.5 × IQR, not 1.5 × range, a swap that costs easy points if you mix them up.
The range is a measure of variability defined in Topic 1.7 as the maximum data value minus the minimum data value. If your data run from 15 to 92, the range is 77, expressed as one number with units.
No. The range is nonresistant (non-robust) because it's calculated from the two most extreme values in the dataset, so a single outlier changes it directly. If Max = 89 while Q3 is only 31, that one point is inflating the range. The resistant measure of spread is the IQR.
Range = Max − Min and measures the full spread including outliers. IQR = Q3 − Q1 and measures the spread of just the middle 50% of the data, so outliers don't affect it. Two datasets can have the same range of 50 but IQRs of 15 and 8, meaning their middles are spread out very differently.
One number. In AP Stats the range is a difference, so write 'the range is 200 square feet,' not 'the range is 100 to 300.' Writing it as an interval is a common everyday-language habit that doesn't match the statistical definition.
Spread. The CED lists range alongside IQR and standard deviation as the three measures of variability for quantitative data. Measures of center are the mean and median, which answer a completely different question about where the data sit.