*LEARNING CHECK*, Ch. 4 material

1. What does *p* stand for?

2. What is the difference between and ?

3. What are two characteristics of a good
sample, when we want to use a sample statistic
to estimate a population parameter?

(Answers below)

Answers:

1. Probability. May be expressed either as a
decimal (.5) or as a fraction (1/2) or percentage
(50%). Decimals are most commonly used. In
statistics, probability means the long-run
relative frequency.

2. (myuu) is the mean of a population (a
parameter) and (x-bar) is the mean of a
sample (a statistic).

3. A random sample is ideal, although
sometimes hard to acquire. Large samples are
better than small samples.

NOTE: In large-scale polling, variations such as
"multistage cluster sampling" are commonly
used that mimic the probabilities of random
sampling. In much psychological research, the
samples are not random, but are samples of
convenience. In these cases, researchers need to
think about how their sample might be different.
Our class may be a reasonable sample of UO
pre-psych majors, for example, but is not a good
sample of Oregonians.