A fundamental statistical test of serial independence is developed and applied to daily stock returns. Let <italic>x</italic> be the deviation of the daily return on a stock from its sample mean after any autocorrelation present has been removed. If <italic>x</italic> is serially independent, then the cumulative sum of <italic>x</italic> over...

Much research has demonstrated the existence of patterns in high-frequency equity returns, return volatility, bid-ask spreads and trading volume. In this paper, we employ a new test for detecting periodicities based on a signal coherence function. The technique is applied to the returns, bid-ask...