9.1-9.7: Statistics Notes:

Below shows the amount of seconds it takes people to settle in a restaurant:

1 5 8 24 28 28 30 32 40 46 47 55 60

Turn into a stem and leaf diagram:

Find the mode, median, mean, interquartile range, and range:

Mode: the most repeated number = 28
Median: midpoint. Since the data is arranged in order you can cross out until you reach the middle = 30
Mean:

4. Interquartile range: quarter 1 - quarter 3 = 46.5 (the average of the 2 middle numbers) − 16 = 30.5

5. Range: maximum - minimum = 60 - 1 = 59

IMPORTANT MEDIAN REMARKS:

If the data is displayed like above or a stem and leaf, you can cross out until the middle. If you get 2 middle values, add them then divide by 2 to get the average
If the data is displayed in a table with class width then divide the sample by 2 and see where that value lies. For example:

This is a sample of 38 ( 20 + 18). Median is the middle so 38/2 = 19. The value 19 lies in the first class.
To find the mean: get the midpoint of each class width and use the same equation

If we want a pie chart for this sample, we divide 360 degrees by the sample (which is 38 in this case)
360/38 = 9.47 deg (this is per 1 person)
The first class width will have 9.47 x 20 = 189.5 deg and the second will have 170.5 deg

Frequency polygons:

Usually the frequency is the y-axis unless stated otherwise in the question
You connect the points in straight lines (like polygons)
If you're working with class width, you take the midpoint and plot. If not, plot immediately. For example: