AP Stats Unit 7

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Statistic vs parameter

SAMPLE statistic
POPULATION Parameter
p=parameter
p̂ (phat)= statistic


statistic or parameter is ANYTHING related to the sammple or population. Could be minimum, could be statistic, could be proportion, like anything

sampling variability

the fact that 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 of the same size from the same population

important to know

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Precise Meaning

Precise correlates to variability. If you are precise, your stuff is clustered. If you’re not precise, it’s spread out a bit more or SD is higher or something of the sort

When n increases, precision increases as well

Accuracy meaning

How close are sample statistics to the population parameter? That is accuracy

SD of sampling distribution of p hat

sqrt(p(1-p)/n)

10% condition

when n or sample size is no more than 10 percent of the population (n</= 0.10N)

Large Counts Condition/Normality Condition

np>/=10 AND n(1-p)>/=10.

When this is met, we can use a normal distribution to estimate the probability of an SRS in which phat lies in a specified interval of values.

mean of sampling distribution

MEan of sampling distribution = mew. like the mean they give you

Standard Deviation of sampling distribution of the sample mean

The standard deviation is the standard deviation they give you divided by sqrt n AS LONG AS the 10% condition is satisfied. n</=0.10N

Central Limit Theorem

when n is large, the sampling distribution of the sample mean is approximately normal (so like usually when n >/= 30).

What happens to sampling distributions of sample means as n increases?

The standard deviation/variability decreases, and the shape gets more and more normal.