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.