The standard deviation of a sample taken from population a is 17.6 for a sample of 25. the standard deviation of a sample taken from population b is 21.2 for a sample of 30. the standard deviation of the sample mean differences is round your answer to the nearest hundredth.

The standard deviation of the sample mean differences should be calculated using the standard deviations of the two populations. In order to see how they differ, we need to first subtract them from each other, so: 21.2-17.6 = 3.6 We then divide this number with the first standard deviation as follows: 3.6/21.2 and multiply this answer by 100. Therefore, the standard deviation of the sample mean is 3.6/21.2 x 100 = 16.98.

Arthropoda and molluscs have open circulatory systems - meaning haemolymph (Their equivalent to blood) directly bathes the tissue, and isn't enclosed in blood vessels, as seen in a closed blood system, as in humans for example.