Dissolved Oxygen (DO) Is an Important Indicator of Water Quality

question 168

Multiple Choice

Dissolved oxygen (DO) is an important indicator of water quality, and oxygen levels that are too high or too low can harm aquatic ecosystems. A biologist noticed that fish were dying in a local lake and was concerned that the DO levels were too low to support aquatic life due to extremely high temperatures that summer. To measure the DO levels, she brought back several lake water samples to her laboratory to measure the DO concentration as a function of temperature. To do this, she heated several samples of lake water to various temperatures and then measured the DO concentration in each sample. Some samples were kept at the outdoors temperature.
Why were some samples kept outdoors?

• A)To minimize researcher bias
• B)To calibrate the thermometer
• C)To allow a maximum amount of oxygen to dissolve before measurement
• D)To act as a control group

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Definitions:

One-Sample Test

A statistical test used to determine whether a sample mean significantly differs from a known or hypothesized population mean.

Hypothesized Proportion Value

A specified value of a population proportion in hypothesis testing that serves as the basis for comparing with the proportion observed in the sample data.

Proportion

A part, share, or number considered in comparative relation to a whole; a fraction or percentage of a total.

Z-Test

A statistical test used to determine whether two population means are different when the variances are known and the sample size is large.