Calculating 95% confidence intervals for systolic and diastolic blood pressure

¶ … calculates the 95% confidence intervals of two data sets, one for the reading of systolic blood pressure and one for the reading of diastolic blood pressure. There was a sample size of 9 total patients included. The steps of reaching the confidence interval are outlined below. Excel was used to find the mean for each data set as well as the standard deviation using the formula provided. From there, the steps were manually calculated.

The confidence interval must be calculated through a number of steps. Some of these were done on excel, while others had to be calculated manually. The first step was to find the average of the data set for each type of blood pressure measured. The systolic average was 131.1 repeating, while the diastolic mean was 75.5 repeating. Next, standard deviation was found using the following formula:

The standard deviation for systolic blood pressure was 23.15407332, while it was 20.68278941 for diastolic blood pressure. The next step was to compute the standard error, which was done by dividing the standard deviation by the square root of the sample size. For systolic blood pressure that meant dividing 23.15407332 by 3, which meant the standard error was 7.7180244. For diastolic blood pressure, the formula was as follows: 20.68278941 / 3, or 6.8942631367. Next, the margin of error was calculated by multiplying the standard error by two. For systolic blood pressure, that meant a margin of error of 15.4360488 and for diastolic a margin of error of 13.7885262734. Finally, the confidence interval was calculated by adding and subtracting the margin of error to the mean of each of the two data categories.