Question

Analyses of drinking water samples for 100 homes in each of two different sections of a city gave the following information on lead levels (in parts per million).
Section 1   Section 2
Sample Size 100 100
Mean 34.3 36.2
Standard Deviation 5.8 6.1

(a) Calculate the test statistic and its p-value to test for a difference in the two population means. (Use Section 1 − Section 2. Round your test statistic to two decimal places and your p-value to four decimal places.)

z =

p-value =

(b) Calculate a 95% confidence interval to estimate the difference in the mean lead levels in parts per million for the two sections of the city. (Use Section 1 − Section 2. Round your answers to two decimal places.)

_____ parts per million to _____ parts per million

Answer 1

a)

Now, the value of test static can be found out by following formula:

Using Excel's function = the P-value for t0 = -2.26 in an t-test with 198 degrees of freedom can be computed as

b) Confidence interval(in %) = 95
z @ 95.0% = 1.96
Since we know that

Required confidence interval = (34.3-36.2-1.6498, 34.3-36.2+1.6498)
Required confidence interval = (-3.5498, -0.2502)