Interval estimation of the population mean can be computed from functions of the following R packages:

stats - contains the t.test;TeachingDemos - contains the z.test; and,BSDA - contains the zsum.test and tsum.test. The t.test of the stats package is a student's t test, and is use when raw dataset is given. The same case for z.test, but this function is specifically for z-test of known population standard deviation. When dataset is not given and only the summary statistics (mean, and standard deviation) are presented, then the appropriate functions are zsum.test or tsum.test. Note that, t.test and tsum.test are functions of the same statistical test, and that of z.test and zsum.test. Consider the example below,

Example 1. The 2012-2013 SASE scores of the 33 random students from College of Science and Mathematics (CSM) of MSU-IIT were recorded: 84, 93, 101, 86, 82, 86, 88, 94, 89, 94, 93, 83, 95, 86, 94, 87, 91, 96, 89, 79, 99, 98, 81, 80, 88, 100, 90, 100, 81, 98, 87, 95, and 94. …

stats - contains the t.test;TeachingDemos - contains the z.test; and,BSDA - contains the zsum.test and tsum.test. The t.test of the stats package is a student's t test, and is use when raw dataset is given. The same case for z.test, but this function is specifically for z-test of known population standard deviation. When dataset is not given and only the summary statistics (mean, and standard deviation) are presented, then the appropriate functions are zsum.test or tsum.test. Note that, t.test and tsum.test are functions of the same statistical test, and that of z.test and zsum.test. Consider the example below,

Example 1. The 2012-2013 SASE scores of the 33 random students from College of Science and Mathematics (CSM) of MSU-IIT were recorded: 84, 93, 101, 86, 82, 86, 88, 94, 89, 94, 93, 83, 95, 86, 94, 87, 91, 96, 89, 79, 99, 98, 81, 80, 88, 100, 90, 100, 81, 98, 87, 95, and 94. …