# AP Statistics Section 11.4 B

```AP Statistics Section 11.4 B
A significance test makes a Type I error
when
it rejects H 0 and the H 0 is really true.
___________________________________
P(Type 1 error ) = ___

A significance test makes a Type II error
when
__________________________________.
it fails to rejects H 0 and the H a is really true
fail to reject H 0
Type II errors are always computed at a
particular value for H a .
Calculating the probability of a Type II error by
hand is possible but unpleasant. It’s better to let
technology do the work for you.
You will not be expected to find P(Type II error)
on the AP exam.
If the probability of a Type II error for a
particular Ha is high, this means that
the test is not sensitive (or tuned-in)
enough to regularly detect that Ha.
power
more sensitive
1- 
Probability of not rejecting
H 0 when H a is true
Calculations of p-values and calculations of
power both tell us what would happen if
the test were repeated many times.
A p-value tells us what would happen
supposing that the ___________,
H 0 is true while
power describes what would happen
supposing a particular __________.
H a is true
When planning a study that will include a
significance test, a careful user of statistics
decides what alternative values of the
parameter the test should detect and
checks that the power is adequate. The
power depends on which particular
parameter value in H a we are interested in.
To calculate power, we must fix an  so
that there is a fixed rule for rejecting H 0 .
Increasing the Power
High power is always desirable.
Along with ____
95% confidence
intervals and ____
5% significance
tests, ____
80% power is becoming a
standard.
The best advice for maximizing the
power of a test is to choose as high an
___level
as you are willing to risk AND

as large a sample size as you can
afford.
increase the probability
of a Type I error
```