1. 6.5 Measures of central tendency
Discrete and continuous data

2. Simple Discrete Data Mode: most frequent Median: middle value
Mean: sum of all values divided by the number of values
Consider the numbers:
Find the mode, median and mean
Use GDC as well

3. Sigma Notation 𝚺 Means “sum of”
𝒓=𝟏 𝒏 𝒓 means “the sum of all values of r from r = 1 up to r = n”
𝒓=𝟏 𝒏 𝒓 = n
Calculate: 𝒓=𝟏 𝟒 𝒓 𝟐

4. Discrete Data in a Frequency Table
Mode is the value with the highest frequency
Median is the middle value
Mean is found by multiplying each value by its corresponding frequency, summing the products and dividing by the sum of the frequencies.
Find the mode, median and mean for the table. X
Frequency
X*frequency 1 4 2 9 3 23 25 5 16 6
Total 80

5. Grouped Discrete or Continuous Data
Modal group/class with largest frequency
Median estimate middle value
Estimated value
To find the mean
Use midpoints multiplied by frequency
Add and divide by cumulative frequency
To find the median Steps
Identify which group it’s in
Decide which entry in that group is the median, a
Find the total frequency of that group, b
Find the width of that group, c
Then use the formula: median = lower limit of group + (a ÷b) x c

6. Find the mode, median and estimated mean.
GDC does NOT give the correct median for grouped data because we use mid-interval numbers
**Must enter each value in group to be accurate.
Time
Midpoint
Frequency
x*f
0≤𝑡<50 20
50≤𝑡<60 61
60≤𝑡<70 83
70≤𝑡<80 90
80≤𝑡<90
106
90≤𝑡<100 62
100≤𝑡<110 49
110≤𝑡<120 29
Total
500

7. Assignment
P.304 #1-7