Week 3 — Readings & Resources · Center & Spread

Course: Introduction to Statistics (MATH 11) · Silver Oak University (fictional sample) · Prof. Rivera
Objective covered: Objective 2 — Summarize and display univariate data: describe its shape, center, and spread.

How to use this page

Everything here is a link to an external resource — open it in your browser, the same way you'd open a YouTube link. Nothing needs to be downloaded.

This week's load is deliberately light: ~4 short readings + ~3 short videos, grouped by the three ideas from the lecture. Read or watch one item per group and you're ready for the quiz; do all of them and you'll be very comfortable. Total time is roughly 40–50 minutes if you do everything, far less if you pick one per group.

Reading order that matches the lecture: ① center — mean, median, mode (and which to use) → ② spread — variance & standard deviation → ③ the five-number summary, quartiles & IQR.

A habit to start now: before you trust any "average" you read below, ask the question from class — what does the data look like? Symmetric data and skewed data call for different summaries, and the readings will keep reminding you why.

① Center · Mean, Median, Mode (and which one is honest)

Maps to Lecture Segments 2–3. The line to carry: the mean chases the outlier; the median ignores it. Match the measure to the shape.

Reading — "Central Tendency | Understanding the Mean, Median & Mode" (Scribbr)
🔗 https://www.scribbr.com/statistics/central-tendency/
Why it's assigned: the cleanest plain-language version of the exact three-way split we drew in class — including a worked outlier example that shows the mean jumping while the median holds, and a table of which measure to use for which kind of data.
⏱ ~7 min

Video — "Mean, Median, and Mode: Measures of Central Tendency: Crash Course Statistics #3"
🔗 https://www.youtube.com/watch?v=kn83BA7cRNM
Why it earns the click: the liveliest tour of the three centers — how they differ, how the gap between them reveals the underlying shape, and how an "average" is sometimes used to mislead (exactly the income-block trap from Segment 3).
⏱ ~12 min

② Spread · Variance & Standard Deviation

Maps to Lecture Segment 4. Remember: center says where, spread says how tightly. The SD is roughly the typical distance of a value from the mean.

Reading — "How to Calculate Standard Deviation (Guide) | Calculator & Examples" (Scribbr)
🔗 https://www.scribbr.com/statistics/standard-deviation/
Why it's assigned: walks the same six steps we did by hand — find the mean, subtract it, square the deviations, add them up, divide (n−1 for a sample), square-root — on a small dataset, so the formula stops being scary and becomes a recipe.
⏱ ~7 min

Reading — "Variability | Calculating Range, IQR, Variance, Standard Deviation" (Scribbr)
🔗 https://www.scribbr.com/statistics/variability/
Why it's assigned: the one-stop overview that puts all the spread measures side by side — range, IQR, variance, standard deviation — and explains when each is the right tool, which ties Segment 4 and Segment 5 together.
⏱ ~8 min

③ The Five-Number Summary · Quartiles & IQR

Maps to Lecture Segments 5–6. The skeleton of the data — Min · Q1 · Median · Q3 · Max — and the resistant spread measure, IQR = Q3 − Q1, that ignores the extremes.

Reading — "How to Find Interquartile Range (IQR) | Calculator & Examples" (Scribbr)
🔗 https://www.scribbr.com/statistics/interquartile-range/
Why it's assigned: shows exactly how to slice sorted data into quarters to get Q1 and Q3, then build the IQR — and explains why the IQR gives a consistent spread even for skewed data, which is the resistance idea from Segment 6.
⏱ ~9 min

Video — "Measures of Spread: Crash Course Statistics #4"
🔗 https://www.youtube.com/watch?v=R4yfNi_8Kqw
Why it earns the click: the single best 11 minutes connecting all the spread measures — range, IQR, variance, and standard deviation — and showing why a resistant measure matters when the data has outliers. Bridges groups ② and ③.
⏱ ~11 min

Video — "Constructing a Box and Whisker Plot" (Khan Academy)
🔗 https://www.youtube.com/watch?v=09Cx7xuIXig
Why it earns the click: a quick worked example that builds a five-number summary from a real dataset and turns it into the picture it describes — a preview of the boxplot we only teased in lecture.
⏱ ~9 min

Optional one-stop reference (free online text)

If you'd like one optional reference to skim all term, OpenIntro Statistics keeps its full text and per-section videos free to read online. Chapter 2 ("Summarizing data") covers everything in this week — measures of center, measures of spread, and the five-number summary.
🔗 https://www.openintro.org/book/os/
Why it's here: a reputable, currently-available reference you can return to in later weeks — entirely optional this week.

Pick-one quick path (≈15 min total)

In a hurry? Do exactly these three and you'll be ready for the quiz:
1. Read Central Tendency (group ①) — the mean/median/mode and which to trust.
2. Watch Crash Course #4 — Measures of Spread (groups ② + ③) — it covers SD and IQR in one go.
3. Read Interquartile Range (group ③) — to lock in the five-number summary.

Heads-up (links rot): these point to outside sites that occasionally move or rename pages. If a link ever fails, tell Prof. Rivera and use the OpenIntro reference above in the meantime.