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Alternative Variance-Ratio Tests Using Ranks and Signs

2000; Taylor & Francis; Volume: 18; Issue: 1 Linguagem: Inglês

10.1080/07350015.2000.10524842

1537-2707

Jonathan H. Wright,

Financial Risk and Volatility Modeling

This article proposes using variance-ratio tests based on the ranks and signs of a time series to test the null that the series is a martingale difference sequence. Unlike conventional variance-ratio tests, these tests can be exact. In Monte Carlo simulations, I find that they can also be more powerful than conventional variance-ratio tests. I apply the proposed tests to five exchange-rate series and find that they are capable of detecting violations of the martingale hypothesis for all five series, whereas conventional variance-ratio tests yield ambiguous results.