Industrial pollution often makes water supplies acidic (pH < 7) or basic (pH >7)
ID: 3370864 • Letter: I
Question
Industrial pollution often makes water supplies acidic (pH < 7) or basic (pH >7). An industrial company claims that the mean pH level of the water in a nearby river is 7, so it is neutral. You, as an environmentalist, randomly select 49 water samples and measure the pH of each. The sample mean and standard deviation are 6.89 and 0.14, respectively. What assumption is necessary for this test to be valid?
None. The Central Limit Theorem makes any assumptions unnecessary.
The sample mean pH level must equal the population mean pH level.
The population of pH levels in all possible water samples is normally distributed.
The population variance must equal the population mean.
Explanation / Answer
since sample size =49 > 30
by central limit theorem
sample mean follow normal distribution
hence
1)None. The Central Limit Theorem makes any assumptions unnecessary. is correct