P HAT

p

X BAR

Mean symbol

s

standard deviation symbol

sampling districution

the distribution of values for a statistic for all possible samples of a given size from a given population.

A good statistic has:

1. Low bias

2. Low variability

Biased

Consistently overestimates or consistently underestimates the true population parameter. (often skewed)

Unbiased

Mean of the sampling distribution is equal to the population parameter.

Parameter

a number that describes some characteristic of the population.

Statistic

a number that describes some characteristic of the sample.

X BAR (the sample mean) ESTIMATES ---->

Mean symbol (the population mean)

P HAT (the sample proportion) ESTIMATES ----->

p (the population proportion)

s (the sample SD) ESTIMATES ----->

SD symbol (the population SD)

sampling variability

different random samples of the same size from the same population produce different values for a statistic

sampling distribution

Distribution of values taken by the statistic in all possible samples (ideal pattern)

variability of a statistic

described by the spread.