A particular characteristic is of interest to a researcher. The researcher is particularly interested in the mean value of this characteristic in the population. A hypothesis test for the mean (u) is to be performed. Select all the pieces of information that are needed in order to calculate the corresponding 2 test statistic: :] the proposed population mean the size of the sample selected the level of significance used the characteristic of interest the sample mean calculated the population standard deviation l_J[_JLlLll_J[_J the actual population mean