Filter
Top Products
Press the STAT key.
Press the ► key twice to highlight TESTS.
Press the number 2 key.
Move the cursor over Stats and press the ENTER key.
Type in 65 for µ
0.
Type in 63 for Ë.
Type in 2 for Sx.
Type in 15 for n.
Move the cursor over <µ
0
and press the ENTER key.
Move the cursor over Calculate and press the ENTER key.
The T-Test output shows the
alternative hypothesis: µ<65
test statistic: t=-3.872983346
p-value: p=8.4464649E
-4
sample mean: Ë=63
sample standard deviation: Sx=2
sample size: n=15
The p-value is 8.446×10
−4
, which is less than 5%. We reject H
0
and conclude that the average
battery lifetime is statistically-significantly less than 65 months
.
Hypothesis Tests About Proportions
Hypothesis tests about proportions are Z-based for sample sizes over 30. The calculator provides
a function called 1-PropZTest that computes a test statistics and p-value. The 1-PropZTest is
located on the STAT page under the Tests list. The menu for 1-PropZTest is very similar to the
one for 1-PropZInt described in the last chapter. Again you need to enter x, the number of
successes, and n, the sample size. You also need to enter p
0
, the number that p is being compared
with, and the alternative hypothesis.
Example: Defective Chips
When working properly, a machine that is used to make chips for calculators does not produce
more than 4% defective chips. Whenever the machine produces more than 4% defective chips, it
needs an adjustment. To check if the machine is working properly, the quality control department
at the company often takes samples of chips and inspects them to determine if they are good or
defective. One such sample of 200 chips taken recently from the production line contained 14
57