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Every part of the classroom

Fifty-five components in the states they can be in, in the order the bundle loads them. Switch the accent to see what a preset changes: actions, links, focus and progress. Callouts, the highlighter and charts stay put.

Buttons

8px buttons in Lexend: slate-teal primary, secondary, ghost, small, large, block, icon-only, toggle, loading and disabled, plus the action group.

Start lesson 1.4

Badges

Small 6px tags for level, week, lesson type and status, a highlighter tag, an outline tag and the count bubble.

  • Beginner
  • Week 2
  • Done
  • Due Friday
  • Overdue
  • Video
  • New this week
  • 14 min
  • 3

Mark

The highlighter: a yellow marker behind a phrase in body text, and a lower swipe for the one marked phrase in a heading.

The standard deviation is in the same units as the data, which is why it is easier to read than the variance. Keep n − 1 for samples.

Spread tells you how far apart the values sit.

Nav

Top bar with the school mark, five links, the theme toggle, a sign-in link and one primary action; folds into a disclosure menu on phones.

Announcement bar

One dismissible line above the nav for enrollment dates and cohort news; remembers the dismissal per visitor.

The January cohort starts January 11. Enroll by January 4.See the schedule

Breadcrumbs

Course, module and lesson path above a page title, with the current page marked.

Sidebar nav

Grouped side navigation for dashboards, help and article topics, with counts and the current item marked.

Hero

Home hero on ruled paper with a coded lesson window (rail, reading column, callout, practice question), plus page and course variants.

Statistics, taught one lesson at a time.

A six-week course for people who use numbers at work and want to trust them. Short lessons, a worked example in every one, and a practice question before you move on.

Next cohort: January 11 to February 19, 2027. Prefer your own pace? Self-paced access starts the day you enroll.

One course, three ways to take it

The lessons are the same in every plan. What changes is the schedule, the live sessions and who reads your capstone.

Section header

Section title in Literata with an optional lede and action; start-aligned, centered or split.

Six weeks, one skill a week

Each module ends with a short quiz, so you know you have it before the next one starts.

What a lesson looks like from the inside

Every lesson follows the same shape: a question, a definition, a worked example, one exam tip, and practice.

Cards

Sheets of paper: plain, linked, ruled index card and desk variants with icon, meta and footer.

  • Lessons you can finish on a break

    Twelve to twenty minutes each, with your place saved, so a lesson fits between two meetings.

  • The n − 1 rule

    Dividing a sample's squared deviations by n − 1 instead of n corrects its habit of guessing the spread too small.

Bento

A six-column grid of study tools, each cell with a coded mini interface in a desk well.

  • Five boxes you learn to read at a glance

    Definitions, worked examples, exam tips, common mistakes and things to remember always look the same, so skimming a lesson before a quiz takes a minute.

  • Flashcards for every term

    Each module ends with a deck. Flip, check, flip back.

  • Study minutes, not streaks

    See which days you studied and for how long. Missing a day costs nothing.

  • Progress by module

    A ring per week shows what's done and what's next.

  • Formulas set like a textbook

    Real fractions and symbols, with every letter explained underneath.

Features

Feature list with icon tiles, and alternating feature rows that pair copy with a coded visual.

  • Practice before you move on

    Every lesson ends with questions that explain the answer, right or wrong.

  • A spreadsheet is enough

    Exercises come in Google Sheets and Excel versions. Python is optional, never assumed.

  • Someone to ask

    Thursday office hours and a cohort space where instructors answer within a day.

Your place, always in view

The lesson rail sits beside every lesson and shows what you've finished, what you're on and what's left in the module.

  • Progress saved after every section
  • Jump to any lesson in the module

Stats

Course facts in big Literata numerals with a short label and note, tabular figures throughout.

weeks
6
Four to five hours a week
short lessons
34
12 to 20 minutes each
practice questions
126
Every answer explained
capstone
1
Your own data, our feedback

Logo row

A row of invented monogram marks for the open data sources the course uses.

Exercises use public data from

  • Harbor City Open Data
  • Westbrook Transit
  • Meadow County Health
  • Linden Weather Station
  • Carver Library Survey

Testimonial

A quote from the school's own people: blockquote, initials avatar, name and role.

We kept meeting smart people who froze at a p-value. Not because the math is hard, but because nobody had taught it in the order you need it. Ridgeway is that order: describe, picture, estimate, then test.

Lena MarshFounder and lead instructor

Pricing

Plan cards with price, inclusions and one primary action, a featured plan and a plain refund note.

Self-paced

All 34 lessons and quizzes, open for a year.

$149one payment
  • Every lesson, quiz and worksheet
  • 126 practice questions with explanations
  • Certificate of completion
  • No live sessions or capstone feedback
Start self-pacedStarts the day you enroll

Team

Five seats in a cohort for a team that learns together.

$1,190five seats, $238 each
  • Cohort access for five people
  • A private kickoff call
  • Progress report for the team lead
  • Invoice and purchase-order billing
Ask about team seatsAdd seats at $238 each

Not for you after the first week? Email us within 14 days for a full refund. No form, no questions.

CTA

Closing call to action on a desk sheet, or the single slate band per page, with a next-cohort line.

Start with lesson 1.4. It's free.

Read it, try the three practice questions, and see if the pace suits you. No account needed.

About 18 minutes, with a worked example and three questions.

Learn it with a cohort this January.

Six Tuesdays of live sessions, office hours every Thursday, and feedback on a capstone built from your own data.

Enrollment closes January 4. Full refund within 14 days.

FAQ

Native details accordion with plus marks, grouped by topic, keyboard and screen-reader friendly without JS.

Do I need to be good at math?

No. You need arithmetic and patience. We use square roots and fractions, and every formula comes with a worked example and one plain sentence that says what it does.

What software do I need?

A spreadsheet. Every exercise has a Google Sheets and an Excel version. Python notebooks are offered as an extra in weeks 4 to 6 and are never required.

What if I fall behind?

Lessons stay open for a year after your cohort ends, and every live session is recorded. Week 5 is lighter by design, so there is room to catch up.

Prose

Long-form reading column in Literata: headings, lists, links, inline code, figures, tables, quotes and the highlighter.

A mean tells you where the middle of your data sits. It says nothing about how far the values stray from it.

Picture two sections of the same class. Both average 72 on the midterm. In the first, nearly everyone scored between 68 and 76. In the second, scores run from 44 to 98. The same mean hides two different classrooms, and that difference is what this lesson measures.

Why not just use the range?

The range, highest minus lowest, is quick. It also depends on only two values, so one unusual score can double it. We want a measure that listens to every value:

  • it should grow when values move away from the mean;
  • it should be in the same units as the data;
  • one outlier should not decide it alone.

A good summary number answers a question you were already asking.

In a spreadsheet, the sample standard deviation is STDEV.S(range). We'll compute it by hand once, so the function stops being a black box.

Callout

The callout taxonomy: definition, worked example, exam tip, common mistake and remember, each with its own bar, tint, icon and label.

Formula

Math set in text with real symbols: variables in italic, fractions, roots, sums and a where-list that names every symbol.

s equals the square root of the sum of squared distances from the mean, divided by n minus 1.
Sample standard deviation
s
the sample standard deviation
xi
each value in the sample
x
the sample mean
n
how many values there are

Table of contents

On-this-page list drawn as a rail: sections you have read are done, the one in view is in progress.

Byline

Author initials, name, role, date and reading time for notes and articles.

Timeline

A vertical rail of dated entries for school history, changelogs and roadmaps, with progress marks for status.

  1. Shipped

    Module 3 rewritten around base rates

    Two new lessons and a worked example built on a medical screening test.

  2. In progress

    Python notebooks for weeks 4 to 6

    Optional notebooks that mirror every spreadsheet exercise, line for line.

  3. Planned

    A seventh module on experiments

    A/B tests, sample sizes and when to stop a test early.

Forms

Labels, hints, inputs, selects, textareas, checkboxes and radios with focus, error, success and disabled states.

Add the part after the @, like [email protected].
Code found: January cohort.
Name the lesson number if your question is about one.
$
How should we reply?
We answer within one working day.

Switch

An on/off setting built on a checkbox with role switch, for reminders and preferences.

Choice cards

Radio or checkbox cards for picking a plan pace, a session time or study goals.

Pick a live session time

Search field

Search box with an icon, a clear button and a submit action, in default and large sizes.

File drop

Drop zone for assignment uploads with a file list, a drag-over state and an error state.

  • bike-share-trips.csv2.4 MB Ready
  • capstone-draft.pagesThis file type is not acceptedNot added

Newsletter

Email sign-up for study notes with inline validation and a polite success message.

One study note every Sunday

A short explanation of one idea, with a worked example and a question to try. Free, whether or not you take the course.

Unsubscribe from any issue in one click.

Tables

Hairline data tables with tabular numerals, a compare variant with check marks, and labelled stacks under 640px.

Module quizzesYour best attempt on each, out of 10
ModuleAttemptsBest scoreStatus
1. Describing data29 / 10Passed
2. Picturing distributions17 / 10Passed
3. Probability you'll use15 / 10Retake open
4. Sampling and the normal curve0Not takenOpens Feb 1
What's includedSelf-pacedCohortTeam
All 34 lessons and quizzesIncludedIncludedIncluded
Weekly live sessionNot includedIncludedIncluded
Capstone feedbackNot includedIncludedIncluded

Description list

Term and value pairs for course facts, certificate details and contact information.

Format
Online, live sessions recorded
Next cohort
to
Time a week
4 to 5 hours
Level
Beginner; arithmetic is enough
Lessons
34
Quizzes
6
Live hours
12

Pagination

Previous, numbered pages and next, with the current page marked and a gap for long runs.

Avatar

Initials on four quiet tints in three sizes, and an overlapping group.

AO LM TR PR LMTRAO

Alert

Inline status messages for info, success, warning and error, with an optional dismiss.

Live session movedTuesday's session starts at 6:30 pm Eastern this week only.
Module 1 completeYour quiz score of 9 out of 10 is saved. Module 2 is open.
Capstone due FridayUpload a draft by 11:59 pm Eastern to get feedback before the final week.

Toast

Short confirmations in a polite live region, raised from any button with data-sy-toast.

Lesson 1.4 marked complete.

Dialog

Native dialog for confirmations such as submitting a quiz, with a scrim, focus return and Escape.

Leave the quiz?

Your 6 checked answers are saved. The 4 open questions will wait for you.

Save and leave

Tooltip

Glossary terms and icon hints that open on hover and focus and close on Escape; never hides essential content.

Half the values fall inside the The distance between the first and third quartiles: the middle 50% of the data., so outliers don't stretch it.

Worksheet 1.4, Excel and Sheets versions

Empty state

A dashed sheet that says what is missing and the one action that fills it.

No notes yet

Highlight a sentence in any lesson and choose "Save to notes". Your notes collect here, grouped by module.

Skeleton

Loading placeholders for cards and lists, with a slow shimmer that stops under reduced motion.

Loading your recommended notes

Progress

Labelled progress bars on native progress elements, and a segmented bar for weeks of a course.

Module 13 of 7 lessons
3 of 7
Practice questions21 of 21
21 of 21
  1. W1 done
  2. W2 done
  3. W3 this week
  4. W4
  5. W5
  6. W6

Progress ring

An SVG ring for module and course completion with the percentage set in the middle.

Chart

Inline SVG bar, line and donut charts that read only the viz tokens, with HTML labels and a data table.

Study minutes per weekFall cohort median, weeks 1 to 6
  • Minutes
  • Week 4 peaks: sampling takes longest
Show the data
WeekMinutes
1180
2210
3165
4240
5150
6195
Quiz scores by moduleYou against the cohort median, out of 100
  • You (modules 1 to 4)
  • Cohort median
Show the data
ModuleYouMedian
18075
27072
39068
46070
5Not yet74
6Not yet71
Where study time goesWeek 2, share of 210 minutes
210minutes
  • Reading lessons40%
  • Practice questions25%
  • Worked examples15%
  • Live session12%
  • Flashcards8%
Study days, last four weeksDarker means more minutes
Less confident after the moduleMore confident
Show the data
WeekStudy daysMinutes
14180
25210
36165
45240

Lesson rail

The signature: a sticky module rail listing lessons with not-started, in-progress and done marks, the current lesson highlighted by JS, collapsible on phones.

Lesson header

Lesson title with the module path, lesson number, time to complete, practice count and the objectives list.

Measuring spread

  • Lesson 1.4 of 7
  • 18 minutes
  • 3 practice questions
  • Updated October 2026

Two data sets can share a mean and look nothing alike. This lesson gives you one number for how spread out values are, and has you compute it by hand once.

By the end of this lesson you can

  • Explain why the range is a weak measure of spread
  • Compute a sample standard deviation by hand for five values
  • Choose between n and n − 1 from the wording of a question

Practice question (MCQ)

Inline practice question: choose, check, see why. Keyboard and screen-reader friendly; without JS the answer sits in a details element.

Practice 1 of 3Two classes both average 72. Which one has the larger standard deviation?
Show the answer

B. Its scores sit 12 to 28 points from the mean of 72, while A's sit 0 to 2 points away. Equal means say nothing about spread, which is why C is the tempting wrong answer.

Practice 2 of 3Quiz times are measured in minutes. What unit is their variance in?
Show the answer

C. Variance averages squared distances, so its unit is squared too. That's why we take the square root: the standard deviation is back in minutes.

Flashcard

Two-sided review cards that flip on click, Enter or Space, with a crossfade under reduced motion and a scrolling deck.

Module 1 terms

4 cards. Select a card to turn it over.

Curriculum

Module accordion with week numbers, lesson counts, durations and the lessons as a rail with type icons and marks.

Week1

Describing data

7 lessons1 h 41 minQuiz: 10 questions
  1. Done1.1Types of data Reading12 min
  2. Done1.2The center: mean, median, mode Reading14 min
  3. Done1.3Shape and skew Video15 min
  4. In progress1.4Measuring spreadFree preview18 min
  5. Not started1.5Percentiles and box plots Reading16 min
Week2

Picturing distributions

6 lessons1 h 28 minQuiz: 10 questions
  1. Not started2.1Histograms that tell the truth Reading15 min
  2. Not started2.2Choosing a bin width Practice12 min

Course card

A course on a coded cover with weeks, level and price, or progress and the next lesson when enrolled.

Instructor card

Instructor sheet with initials, role, a short bio and office hours.

Lena Marsh

Founder and lead instructor

Spent eleven years as a survey statistician for a county health department, explaining confidence intervals to people who had a budget meeting in an hour. Writes Modules 1 to 3.

  • Teaches Modules 1 to 3
  • Office hours Thursdays, 12:30 pm Eastern

Tomás Reyes

Instructor

Taught introductory statistics at a community college for nine years and still grades every capstone by hand. Writes Modules 4 to 6.

  • Teaches Modules 4 to 6
  • Answers the cohort space on weekdays

Schedule

Cohort calendar list: weeks with dated live sessions, office hours and deadlines, past ones marked done.

Week 4 Nov 2 to 6, 2026

  1. Live session: the normal curve6:00 pm Eastern · 60 min · recording postedAttended
  2. Office hours with Tomás12:30 pm Eastern · 45 minAttended

Week 5 Nov 9 to 13, 2026

  1. Live session: confidence intervals6:00 pm Eastern · 60 minNext
  2. Office hours with Lena12:30 pm Eastern · 45 minOffice hours
  3. Capstone draft due11:59 pm EasternDue

Lesson pager

Previous and next lesson cards at the end of a lesson, with a mark-complete action.

Quiz summary

Quiz question rail and the results panel: score ring, per-question marks and links back to the misses, kept live by JS.

50%so far

5 of 10 correct

4 still open. Check each answer as you go; the score fills in here.

Certificate

A printable certificate of completion with a seal, signatures, a verification line and print styles.

Ridgeway School of Data

Certificate of completion

This certifies that

Priya Raman

has completed Practical Statistics, a six-week course of 34 lessons, six module quizzes and a capstone analysis reviewed by an instructor.

  1. CompletedM1
  2. CompletedM2
  3. CompletedM3
  4. CompletedM4
  5. CompletedM5
  6. CompletedM6
Lena MarshLena MarshFounder and lead instructor
RidgewayFeb 19, 2027
Tomás ReyesTomás ReyesInstructor, Modules 4 to 6
Certificate RSD-2027-0219-4471. Verify at ridgeway.example/verify

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