Hypothesis Testing
Hypothesis Testing
• We talked about this the first day.• Let’s talk more about it now.• Four steps:
– Formulate Null hypothesis and Alternative hypothesis (hypothesis)– Obtain sampling distribution and rejection regions (population)– Calculate test statistic from your data (sample)– Compare the test statistic to rejection regions
(if within rejection region, then significant)
Hypothesis
• Formulate Null and Alternative hypothesis
– Null hypothesis H0 : Population means equal
• If two groups: 1 =
• If three+ groups: 1 = ==
– Alternative hypothesis: H1 : mean NOT equal
• If two groups:: 1 ≠
• If three+ groups: 1 ≠ ≠≠
As a researcher, you want to reject the “null”.
Errors in Hypothesis TestingREALITY
OU
TP
UT
FR
OM
SP
SS
H0 is true (n.s.)
Reject H0
(sig)
H0 is false (sig)
Fail to Reject
H0
(n.s.)
Probability =
Probability = (1 - ) (test statistic is not in
Rejection region)
(test statistic is in
Rejection region)Type I error, or “False Alarm”
Correct Decision
Probability = (1 -
Probability =
Correct Decision
Type II error,or a “miss”
POWER
Factors Increasing Power:
(1) Increasing alpha level (e.g., .05 to .09)
(2) Increasing difference between means
(3) Reducing between-group variation
(4) Increasing sample size