TOPIC 2 · MAJOR ASSIGNMENT 1 · COMPONENT 01 / Conversions & Budgeting / major assignment / income analysis

01Slope, intercept, and a line that predicts.

Fit a best-fit line to BLS data on years of education vs. weekly income, then use that line to predict incomes for years 8 through 24. Build the scatter plot and extend the trendline both directions.

Major Assignment · 23 pts Excel · desktop only =SLOPE() · =INTERCEPT()
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A 7-page MA1 Walkthrough PDF covers all three tabs in the same hint depth as this page. Useful if you'd rather print, annotate on paper, or keep it open on a second screen while working in Excel.

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1
Step 1 · materials
Download the worksheet

Topic_2_MA_1.xlsx

XLSX
2
Step 2 · walkthrough
Watch the click-by-click

Walkthrough video coming in a future recording. Until then, work from the slideshow above and the printable PDF.

SCRIBE.HOW · YOUTUBE
Step-by-step walkthrough
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Video walkthrough
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Same walkthrough, two modes. Use whichever helps you today.
ORIENT · the tab

Three sections, one workflow.

BLS data on top. Your predictions below. Chart at the bottom.

Your name in cell B1 seeds the data — until you fill it in, every value in column B reads “Enter your name in B1.” Type your full first and last name first, then everything below populates.

§1 · BLS data

Column A (Years), Column B (Income).

Eight rows. Column A holds years of education (X). Column B holds the corresponding average weekly income (Y), randomized off your name.

§2 · Predicted incomes

Column D (Years 8–24), Column E (Predict).

Column D is already filled. Column E is where you'll use the line equation Y = m·X + b to predict income at each year of education.

§3 · Scatter plot

Inserted below the data tables.

Empty for now. You'll insert an XY scatter of the BLS data (columns A and B, not the predicted table) with a trendline extended to x = 8 and x = 24.

CONCEPTS · six things to know

The four moves you'll make.

Each is the same Excel pattern: click cells, never type numbers. Lock the references with dollar signs so formulas copy clean.

01
Slope

=SLOPE() reads rise over run, automatically.

Type =SLOPE(Y-range, X-range)Y first, X second. Y is your Average Weekly Income column (B). X is Years of Education (A). The function returns the slope of the best-fit line through every (X, Y) pair in the data.

Format the result cell as Number with 0 decimals. The number tells you how many extra dollars per week each additional year of education buys.

02
Intercept

=INTERCEPT() finds b.

Same shape as SLOPE: =INTERCEPT(Y-range, X-range), Y first. INTERCEPT returns the predicted Y-value when X = 0 — where the best-fit line would cross the y-axis if extended.

Format as Number with 0 decimals. Read it as “the predicted weekly income at zero years of education” — which is a wild extrapolation, so don't treat the value too literally. It's a parameter, not a real-world prediction.

03
Predict

Plug the line equation into every row of column E.

The pattern: =$slope_cell * D_cell + $intercept_cell. Lock the slope and intercept cells with $ signs (e.g., $B$28) so the formula copies cleanly down. The D-cell stays relative so each row picks up its own X-value.

Format column E as Currency with the $ symbol and 0 decimals.

=$slope * D-cell + $intercept
Slope and intercept locked with $. D-cell stays relative.
Copy down column E from row 19 to row 35.
04
Chart

Scatter plot the BLS data only, then add the trendline.

Highlight columns A and B (just the eight data rows). Insert → Chart → XY Scatter. Don't include the predicted-incomes table — that's a separate exercise.

With the chart selected: Chart Design → Add Chart Element → Trendline → Linear. Then right-click the line and pick Format Trendline. Set Forward forecast so the line reaches x = 24, and Backward forecast to reach x = 8. Add a chart title and axis labels via Add Chart Element.

Common slips

Four mistakes that cost the most points.

Check these before you submit. Three out of four are formula-reference issues, not math errors.

  1. 01
    SLOPE arguments reversed.

    =SLOPE(X, Y) returns the reciprocal of the right answer (~0.16 instead of ~6). Y first, X second. ALEKS reads it like “rise over run.”

  2. 02
    Predicted-incomes formula hand-typed the slope and intercept.

    Looks right on the surface, but the auto-grader checks for cell references. Click the slope and intercept cells in your formula instead of typing the numbers. Add dollar signs ($B$28) so references don't shift when you copy down.

  3. 03
    Charted the wrong range.

    If your scatter plot has dots at (8, 0), (9, 0), … you selected the predicted-incomes table (D and E) instead of the BLS data (A and B). Click the chart, “Select Data,” and point at columns A and B for the BLS data only.

  4. 04
    Trendline doesn't extend to 8 or 24.

    Right-click the trendline → Format Trendline. Set Forward forecast and Backward forecast so the line reaches from x = 8 to x = 24, even though the data only spans 10–20.

Application & connection

This is Topic 1, in spreadsheet form.

Slope and y-intercept are the Topic 1 move. The Excel functions =SLOPE() and =INTERCEPT() just automate what you'd do by hand with two points: divide rise by run, then back-solve for b. Read your output as a story: the slope tells you how many extra dollars per week each year of education buys, and the intercept is the predicted income at zero years (which is a wild extrapolation, hence the chart's lower bound at 8).

If the math feels distant, jump back to Topic 1 Lesson 4 (Slope) and Lesson 5 (Linear Modeling) for a refresh. The Excel shape is also very similar to Topic 1 DQ 1: cell references in formulas, gold cells for the math, blue cells for text, number formatting at the end.