Petroleum pollution in oceans is known to increase the growth of a certain bacteria. Brian did a project for his ecology class in which he made a bacteria count (per 100 milliliters) in nine random samples of sea water. His counts gave the following readings:

17, 23, 18, 19, 21, 16, 12, 15, 18

a) Find the range.

b) Find the sample mean.

c) Find the median.

d) Find the mode.

e) Find the sample standard deviation.

**Solution:**

**a) **The range is 21 - 12 = 9.

**b) **The sample mean is_{}

**c) **The median is 17.5 as well.

**d) **The mode is 18.

**e) **The sample standard deviation is_{}

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