Both a gravimetric and a spectrophotometric method are under consideration for determini...

Both a gravimetric and a spectrophotometric method are under consideration for determining phosphate content of a particular material. Six samples of the material are obtained, each is split in half, and a determination is made on each half using one of the two methods, resulting in the following data. Use an approximate 95% distribution-free confidence interval to estimate the mean difference for the two techniques. Interpret the interval.