Load-bearing structures in underground mines are often required to carry additional loads while mining operations are in progress. As the structures adjust to this new weight, small-scale displacements take place that result in the release of seismic and acoustic energy, called rock noise. Assume that in a particular mine the average number of rock noises recorded during normal activity is 3 per hour. Would you consider it unusual if no more than 2 were detected in a 2-hour period