## Idempotency of linear combinations of two idempotent matrices.(English)Zbl 0984.15021

The authors give a complete solution for the problem of characterizing all situations, where a linear combination $$P=c_1P_1 +c_2P_2$$ of two different idempotent matrices $$P_1$$ and $$P_2$$ is also an idempotent matrix. They point out a statistical interpretation of this idempotency problem.
Reviewer: T.Nono (Hiroshima)

### MSC:

 15B57 Hermitian, skew-Hermitian, and related matrices 62H10 Multivariate distribution of statistics

### Keywords:

chi-square distribution; idempotent matrices
Full Text:

### References:

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