The main criteria in deciding the use of a z-test or a t-test will be the size of the data set. If the sample size is small (<30) perform a t-test, if the sample size is larger (>= 30) perform a z-test.

When doing a test, steps to be covered:

1. state the hypothesis and identify the claim
2. find the critical value from the table
3. compute the test value
4. make the decision to reject or not the null hypothesis

STATE ALL WORK AND EXPLAIN WHY YOU ACCEPT OR REJECT THE NULL HYPOTHESIS

One sample T-Tests as CIE. We will use the following formulaSHOW ALL WORK

PROBLEM 3 :

The Fresh Springs Company claims that there is less than 1 ppm (parts per million) of benzene in their water. Test at a=.10

n=25

= 1.10 ppm

s = .20 ppm

PROBLEM 4

You want to estimate the average life of a new kind of computer chip.You take a sample of 16 chips and find the sample mean to be 10 years with a sample standard deviation of .80 years.You construct a 90% two-sided confidence interval estimate.It is:_________________