AP Stats 8.3 & 10.2

What is t* used for?

To estimate means

degrees of freedom

The number of individual scores that can vary without changing the sample mean. Statistically written as 'n-1' where n represents the number of subjects.

Conditions

1. Random

2. 10% - n<0.1N

3. Normal:

Population distribution is approximately normal (stated in problem) OR

n>=30, Central Limit Theorem OR

n<30, look at dot plot and show it! Sample data shows NO strong skew and NO outliers

Construct confidence interval for mean

1. Choose: procedure, parameter, confidence level, statistic and degrees of freedom

2. Check conditions

3. Calc: General and specific formulas, work, answer

4. Conclude

Interpret confidence interval

We are ____% confident that the interval from _____ to ______ units captures the true parameter (context)

What is the t-distribution used for?

Estimating population parameters for small sample sizes or unknown variances

Is there convincing evidence of a difference in means?

(-,-) Yes evidence

(-,+) No evidence

(+,+) Yes evidence

What are the 3 possible procedures from this unit?

1. One sample t-interval for M

2. One sample t-interval for Mdiff

3. Two sample t-interval for (M1-M2)

Margin of Error

t* (SE)