Question

A certain chemical pollutant in the Genesee River has been constant for several years with mean μ = 34 ppm (parts per million) and standard deviation σ = 8 ppm. A group of factory representatives whose companies discharge liquids into the river is now claiming that they have lowered the average with improved filtration devices. A group of environmentalists will test to see if this is true at the 4% level of significance. Assume that their sample of size 50 gives a mean of 32.5 ppm. Perform a hypothesis test (6 step procedure outlined in class) at the 5% level of significance and state your decision.

Answer 1

This is the left tailed test .

The null and alternative hypothesis is

H₀ : = 34

H_a : < 34

Test statistic = z

= ( - ) /    / n

= (32.5 - 34) / 8 / 50

Test statistic = -1.33

P-value = 0.0918

P-value >

Fail to reject the null hypothesis .

There is not sufficient evidence to conclude that the river is now claiming that they have lowered the average with improved filtration devices