*Final Answer:
The null hypothesis (H0): The average dissolved oxygen (DO) level in the stream is equal to or above 5 mg/L.
The alternative hypothesis (H1): The average DO level in the stream is below 5 mg/L.
Since the p-value is less than 0.05 (α=0.05), we reject the null hypothesis.
Step-by-step explanation:
The researcher conducted a hypothesis test to determine if the average dissolved oxygen (DO) level in the stream is below 5 mg/L, a critical threshold for aquatic life. The null hypothesis (H0) assumes that the average DO level is equal to or above 5 mg/L, while the alternative hypothesis (H1) suggests it is below 5 mg/L.
The researcher calculated the average DO level from 15 randomly chosen locations along the stream and obtained a value of 4.77 mg/L. To assess the significance of this result, the researcher compared it to a significance level (α) of 0.05, a common threshold in hypothesis testing.
The p-value represents the probability of obtaining results as extreme as the observed average DO level, assuming the null hypothesis is true. In this case, the p-value is less than 0.05, indicating that the observed average DO level is statistically significant. Therefore, there is enough evidence to reject the null hypothesis.
Consequently, the conclusion is that, at a 5% significance level, the average DO level in the stream is below 5 mg/L. This finding raises concerns about the water's ability to support aquatic life, emphasizing the importance of monitoring and addressing dissolved oxygen levels in the stream.