# Analyzing a Frequency Distribution

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The frequency distribution below shows the distribution for suspended solid concentration (in PPM) in river water of 50 different waters collected in September 2011.

Concentration (PPM) Frequency

20-29 1

30-39 8

40-49 8

50-59 6

60-69 16

70-79 7

80-89 2

90-99 2

1. What percentage of the rivers had suspended solid concentrations less than 50?

2. Calculate the mean of this frequency distribution.

3. In what class interval must the median lie? Explain your answer (you don't have to find the median).

4. Assume that the largest observation in this data set is 98. Suppose this observation were incorrectly recorded as 988 instead of 98. Will the mean increase, decrease, or remain the same? Will the median increase, decrease or remain the same? Explain your answers.

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##### Solution Summary

An analysis of frequency distributions are provided.

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1. What percentage of the rivers had suspended solid concentration less than 50?

Answer: We can see that there are 1+8+8=17 waters whose solid concentration is less than 50 and there are 50 different waters total. So percentage of the rivers that had a suspended solid concentration less than 50 is 17/50=34%.

2. Calculate the mean of this frequency distribution.

Answer: We need to first calculate the midpoint of each interval and then multiply that midpoint with frequency

interval midpoint ...

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