Question

A researcher for the EPA measured the amount of arsenic in the water near a sewage treatment plant. Over 12 days, he took n = 40 measurements (in ppb). His sample data is summarized in the frequency polygon shown below. How many measurements taken in this time frame were within (30, 35) ppb?

Answer 1

To find the number of measurements within the range (30, 35) ppb, subtract the number of measurements below 30 ppb from the number of measurements below 35 ppb.

Step-by-step explanation:

To determine the number of measurements taken within the range of (30, 35) ppb, we need to examine the frequency polygon provided in the question. The frequency polygon shows the number of measurements falling within different range intervals. In this case, the range (30, 35) ppb is not directly represented in the frequency polygon. However, we can calculate the number of measurements within this range by subtracting the number of measurements falling below 30 ppb from the number of measurements falling below 35 ppb.

Let's assume there are x measurements below 30 ppb and y measurements below 35 ppb. We can determine these values by examining the frequencies associated with the intervals below 30 ppb and below 35 ppb in the frequency polygon. Then, we can find the desired number of measurements within the range (30, 35) ppb by subtracting x from y.

Answer 2

we can see that 4 measurements were taken in this time frame were within (30, 35) ppb.

In a frequency distribution, each bar represents the number of measurements falling within a specific range. In this case, the range is (30, 35) ppb. The notation (30, 35) indicates that 30 ppb is included, but 35 ppb is excluded.

The bar for the range (30, 35) ppb has a height or frequency of 4 means that there were 4 measurements taken during the time frame that fell within the range from 30 ppb (inclusive) to 35 ppb (exclusive).