February 13

Goal ­ Calculate and interpret a confidence Interval
Part 1 - calculate an upper critical t score (t*)
1. Sketch a semi - normal curve (floating), add the
confidence level into the curve
2. Subtract to find the area
outside the confidence level.
3. Add to find the area to the left of
the desired t score (t * ). This is
called the upper critical t score
4. Look up the t score for the given area.
This is a backwards table problem
OR use the t-AREA (add degrees of freedom)
program in your calculator. This is the desired t *
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