3.2 Day II: Measures of Central Tendency By the end of class you will be able to calculate the frequency table mean and weighted mean, and all measures of central tendency by using a calculator.

Frequency Table Mean Used when the given data are presented in a frequency table. Must use class midpoints instead of actual raw data.

Presidential Inauguration Age

Presidential Inauguration Age Modal Class

Weighted Mean Mean computed by assigning data different weights w = weight, x = data value First test: 85, counts for 20% of grade Second test: 90, counts for 30% of grade Third test: 75, counts for 50% of grade

Journal Reflection Write down anything you think you need to remember to calculate a frequency table mean or weighted mean.

Central Tendency & Calculator For mean & median enter the raw data in L1 In the Stat menu calculate 1-variable statistics Do not round until the final answer Round to one more decimal place than the original data

Frequency Table Mean & Calculator Enter Class midpoints in L1 Enter Frequencies in L2 In Stat menu calculate 1 var statistics (L1,L2)

Weighted Mean & Calculator Enter data values in L1 Enter weights in L2 In stat menu calculate 1 vars statistics (L1, L2)

Find the mean, median mode and midrange (age of thieves in a jail) 18 16 23 25 19 18 20 38

Find the Frequency Table Mean and Modal Class

Find the Weighted Mean (GPA) Math: 3 credits A (4points) English: 3 credits B (3 points) Biology: 4 credits B (3 points) Gym: 2 credits C (2 points)

Measures of central tendency and distribution shape The shape of the distribution affects the location of the mean, median and mode

Symmetric Distribution Data values are evenly distributed on both sides of the mean When the distribution is unimodal, the mean, median and mode are the same and located at the center.

Right Skewed Order of central tendencies: mode, median, mean Majority of data located to left of mean

Left Skewed Order of central tendency: mean, median, mode Majority of data values to the right of the mean