Answer:
C) Reject if t < -1.711
Step-by-step explanation:
We are given that a certain chemical pollutant in the Arkansas River has been constant for several years with mean μ = 34 ppm (parts per million).
Also, it is given that the level of significance is 0.05 and a sample size of 25 is taken.
<u><em>Let </em></u><u><em> = average chemical pollutant in the Arkansas River</em></u>
So, Null Hypothesis, : = 24 ppm {means that the average is same as before with improved filtration devices}
Alternate Hypothesis, : < 24 ppm {means that they have lowered the average with improved filtration devices}
Now, t test statistics is given by; T.S. = ~
where, n = sample size = 25
n - 1 = degree of freedom = 25 - 1 = 24
Now, at 0.05 significance level in the t table, the critical value at 24 degree of freedom is given as - 1.711 for left tailed test.
So, we will reject our null hypothesis when the t test statistics is less than the critical value of t which means reject null hypothesis if t < -1.711.