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Paired-return centered-sum bridge

The original five-period record gives slope 2.1 and intercept 1.2% with SSE 1.2 percentage points squared.

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Keep the original paired record

Original hypothetical period returns
PeriodBenchmark (%)Asset (%)
1-2-3
2-1-0.5
301
412.5
526

Compute the centered sums

Benchmark mean is 0% and asset mean 1.2%. Benchmark deviations are −2/−1/0/1/2; asset deviations are −4.2/−1.7/−0.2/1.3/4.8 percentage points. Their cross-products sum to 21 and benchmark squares to 10.

Recover fitted values and deviations

Original fit bridge
PeriodFitted (%)Residual (percentage points)
1-30
2-0.90.4
31.2-0.2
43.3-0.8
55.40.6

Reconcile both fitting identities

Residuals 0/0.4/−0.2/−0.8/0.6 sum to zero, and their benchmark-weighted sum is also zero. Squared residuals sum to 1.2. Those identities verify the supplied least-squares calculation, not statistical assumptions about future errors.

Further references