Chapter 22b
Hypothesis testing on means
Step 1. Write the null and alternative hypotheses
Null: Always contains an = sign and CONTAINS THE VALUE FOR “
μ
”
The null states what is currently going on in the population.
Alternative: Always contains an <,>, or
≠
The alternative states what the researcher believes is true.
Step 2. Determine
X
, s and n BASED ON THE STUDY
Step 3. Plug
X
,
μ
, s and n into the formula:
Z=
X
sn
μ
−
Step 4. Look up the Z-score on the chart to find the associated percentile
(remember this is already a percent…do not slide the decimal point!!!!!!)
Step 5. Find the P-value
If the alternative hypothesis in step 1 is a “less than” statement, the percentile is the p-
value.
If the alternative hypothesis in step 1 is a “greater than” statement, you must subtract the
percentile from 100 to get the p-value
Step 6. Draw the conclusion
If the p-value is less than 5% (or .05), then reject the null in favor of the alternative.
Acknowledge you may have made a type I error.
If the p-value is greater than 5% (or .05), then fail to reject the null. Acknowledge you
may have made a type II error.