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Mathematics · unit version 1

Statistical investigations, simulation and probability decisions

School-entry workflows that construct displays, inspect fitted models, develop simulation evidence and justify probability-based decisions. Original synthetic practice is labeled; public artifacts and written reports require review and do not certify mastery.

Open any lesson. Completion records participation; automatic practice checks and human judgment of written arguments are separate. This unit retains its own versioned requirements.

Readiness and preparation

Check your starting point

Try these short questions on paper, then compare your reasoning. They are optional self-checks, not a placement score or a navigation requirement. Use a targeted review when useful and return with your browser’s Back control.

Why can two groups have the same mean but different shapes?

A single summary cannot replace a display of the observations.

Compare reasoning and find a refresher

The groups 0,5,10 and 4,5,6 both average 5 but have different spread. Inspect the values and their context before choosing a summary.

Review center, spread and robustness

What is a residual?

Comparing models requires a consistent sign and scale.

Compare reasoning and find a refresher

Residual means observed y minus predicted y for the same x. A positive residual is an observation above its prediction; a patterned residual plot can reveal a model mismatch.

Review fitted lines and residuals

How do random sampling and random assignment differ?

The two simulation workflows answer different questions.

Compare reasoning and find a refresher

Sampling selects who is observed from a population. Assignment chooses who receives which treatment among participants. Random assignment alone does not make participants representative of a population.

Review study design and scope

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Produce and defend a statistical investigation

The mixed assessment has separate response history and review criteria; it does not change lesson participation records.

Lesson sequence

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  1. Construct three views of one dataset

    Lesson details and objectives

    Build a dotplot, histogram and boxplot and document the choices that make their meanings reproducible.

    • Construct a dotplot and a fully labeled histogram from raw values.
    • Build a boxplot using a declared quartile and whisker convention.
    • Diagnose bin-boundary, density and outlier-display errors.

    6 practice tasks.

  2. Compare shapes before choosing summaries

    Lesson details and objectives

    Use supplied observations and constructed displays to compare skew, center, spread and unusual values in context.

    • Compare distributions with common-scale displays.
    • Choose and justify robust or nonrobust summaries for contrasting shapes.
    • Explain how unusual values and sampling scope affect a contextual conclusion.

    6 practice tasks.

  3. Check a normal model against raw observations

    Lesson details and objectives

    Estimate center/spread with technology, inspect fit and qualify a normal-area calculation.

    • Calculate a sample mean and sample standard deviation from raw data.
    • Assess a normal approximation using shape, unusual values and sampling context.
    • Use a supplied normal table or technology to estimate a population percentage with limitations.

    6 practice tasks.

  4. Calculate and interpret Pearson correlation

    Lesson details and objectives

    Use a reproducible technology workflow for nontrivial Pearson correlation and explain its limits.

    • Calculate Pearson correlation from an entered paired dataset and verify intermediate sums.
    • Interpret correlation with a scatterplot, units and contextual limits.
    • Diagnose constant-variable, unusual-point and nonlinear cases.

    6 practice tasks.

  5. Compare fitted models and plotted residuals

    Lesson details and objectives

    Fit three candidate families, compare errors on the same response scale and inspect residual structure.

    • Compare linear, quadratic and exponential fits using the same observed responses.
    • Construct residual plots and diagnose systematic patterns.
    • Interpret contextual coefficients and restrict predictions to justified domains.

    6 practice tasks.

  6. Develop a margin from repeated samples

    Lesson details and objectives

    Calibrate an empirical error margin with repeated random samples and test it on separate trials.

    • Develop a finite-simulation margin from absolute sampling errors.
    • Evaluate a fixed calibrated margin using independent simulation draws.
    • Connect a survey interval to its sampling assumptions and distinguish Monte Carlo variability from survey uncertainty.

    6 practice tasks.

  7. Simulate treatment reassignment under a null

    Lesson details and objectives

    Build a sharp-null assignment distribution and compare a seeded approximation with exact enumeration.

    • Simulate the original random assignment mechanism under a sharp null.
    • Record assignments, test statistics and a prespecified tail rule.
    • Compare Monte Carlo and exact reference results while limiting causal and population claims.

    6 practice tasks.

  8. Count ordered and unordered selections

    Lesson details and objectives

    Define equally likely outcomes before choosing permutations or combinations.

    • Use permutations for distinct roles and combinations for unordered groups.
    • Calculate compound-event probabilities with an explicit denominator.
    • Diagnose ordering, replacement and unequal-selection errors.

    6 practice tasks.

  9. Map outcomes to a probability distribution

    Lesson details and objectives

    Map elementary outcomes to a numerical variable and graph its probability law.

    • List elementary outcomes and map each to a value of a random variable.
    • Aggregate repeated values into a normalized mass distribution and graph.
    • Compute and interpret an expectation including a net-payoff transformation.

    6 practice tasks.

  10. Build a forecast from observed frequencies

    Lesson details and objectives

    Turn observed frequencies into an inspectable forecasting model and identify its limits.

    • Construct an empirical mass table and graph from observed counts.
    • Calculate an empirical expectation and distinguish it from a known generating law.
    • Evaluate sample scope, missing outcomes and changing conditions before forecasting.

    6 practice tasks.

  11. Compare uncertain strategies and consequences

    Lesson details and objectives

    Compare expected consequences while preserving uncertainty, thresholds and risk preferences.

    • Calculate and compare several strategy expectations from an explicit payoff table.
    • Find probability or cost thresholds where the preferred strategy changes.
    • Use conditional risk and consequence data without reducing every decision to expectation alone.

    6 practice tasks.

  12. Design and audit a fair random allocation

    Lesson details and objectives

    Design equal-chance procedures and account for rejection, finite limits and implementation bias.

    • Construct an equal-probability allocation from a specified random source.
    • Prove fairness including rejected draws, ties and bounded failures.
    • Audit the difference between equal chances, equal realized counts and other fairness goals.

    6 practice tasks.