3. In an evaluation of a method for the determination of fluorene in seawater, a synthetic sample of seawater was spiked with 50 ng ml-1 of fluorene. Ten replicate determinations of the fluorene concentration in the sample had a mean of 49.5 ng ml-1 with a standard deviation of 1.5 ng ml-1. Calculate the 95% confidence limits of the mean. Is the spiked value of 50 ng ml-1 within the 95% confidence limits?