1. Means & Medians

2. Parameter -Fixed value about a population
Typically unknown
Statistic –Value calculated from a sample

3. Measures of Central Tendency
Median - the middle of the data; 50th percentile
Mean - the arithmetic average
Mode – the observation that occurs the most often
If all values occur only once – there is no mode

4. Using the calculator . . . Press Stat and chose option 1: Edit
Clear anything in the list and enter your values into L1
Hit 2nd Quit to get back to the home screen
Hit 2nd Stat (List)
Move to Math and chose the option you would like to compute
Inside the parenthesis you must tell it what list to use. (in this case we are using L1). Then press enter.

5. Resistant - YES NO Statistics that are not affected by outliers
Is the median resistant?
YES
Is the mean resistant? NO

6. In a symmetrical distribution, the mean and median are equal.
In a skewed distribution, the mean is pulled in the direction of the skewness.
In a symmetrical distribution, you should report the mean!
In a skewed distribution, the median should be reported as the measure of center!

7. Graphs Used for Categorical Data
Bar graphs
Pie charts

8. Graphs Used for Quantitative Data
Dotplots
Stem and leaf Plots
Histograms
Just like a bar graph
Usually no space between the bars

9. Describe the overall pattern of a distribution
Center
Unusual (outliers)
Spread
Shape

10. Shape …
Symmetric – distribution is symmetric when left and right sides of histogram are approximately mirror images of each other
Skewed to the right – right side is LONGER than the left
Skewed to the left – left side is LONGER than the right

11. Spread
There are various ways to describe the spread of a distribution:
Range
Variance
Standard Deviation
Quartiles
Etc….

12. Work on Graphs Practice sheet