1. Ten things about Inference
AP Statistics, Second Semester Review

2. Population vs. Sample µ, mean σ, standard deviation p, proportion
ρ, coefficient of correlation
β, slope
x-bar, mean
s, standard deviation
p-hat, proportion
R, coefficient of correlation
b, slope

3. Census vs. Sample What we want… What we can easily find out…
To know what is going on at the population level
What we can easily find out…
What is going on at the sample level
What we plan for…
That representative sample will allow us to make statements about the population without actually doing a census

4. In General
Sampling creates statistic which is an estimate to some unknown population parameter
That statistic can be used to create an interval in which we think the population parameter exists Or
That statistic can be used as evidence against some claim

5. Decisions, Decisions Z-Test T-Test 1-Prop Z-Test 2-Sample Z-Test
2-Sample T-Test
2-Prop Z-Test
LinReg Test
Chi-square GOF Test
Chi-square Test
Z-Interval
T-Interval
1-Prop Z-Interval
2-Sample Z-Interval
2-Sample T-Interval
2-Prop Z-Interval

6. What do we mean by significant?
When we say the test was significant at the α=.05 level, we mean…
When we assume H0 is true
these sample results (or more extreme)
would happen by chance
less than 5% of time

7. How do we interpret 95% confidence interval?
“With 95% confidence, we believe the true parameter from the population of interest lies between these two values.”
Replace the word parameter with the parameter used in context
Replace the words population of interest with the context

8. What do we mean by 95% confident?
That if we performed this sampling
with the same sample size
on the same population
many, many times
and calculated the confidence interval each time
95% of the confidence intervals would include the parameter that we were trying to estimate
Probability