Reading Assignments:
- Reread Babbie, Chapter 14
- Descriptive
Statistics. These are descriptive statistics for
continuous variables: mean, median, mode and standard
deviation. We will also do row, column and total percents from
crosstabulation tables using categorical data. This is covered in
the notes below.
- Statistics
Overview.
Class Notes:
The EXCEL file with the computations
of descriptive statistics done in class on Wednesday is here.
Descriptive statistics describe the sample. There are two
types: those for continuous data and those for categorical data.
Here are some categorical data. There are two variables:
gender and liking for spinach.
45 men like spinach
85 women like spinach
65 men do not like spinach
80 women do not like spinach
Our first step is to put them in a table with the Independent
Variable
in the Column and the Dependent Variable in the Row
Men women
Like
45
85 130
Don't
65
80
145
110
165
275
With this table, we can answer questions. Some are percent
questions, some are frequencies questions. We will do these in
class and I will be adding the answers to this WEB page.
How many respondents like spinach? the base of the % is the word
after how many, in this "respondents". The numerator is the
number in the next clause, those who like spinach.
130/275 =.4727 This is the proportion, or the probability
that any one respondent will like spinach. Percent meeans per
100. We multiply by 100. Then we allow one number after the
decimal, rounding off, and add the % sign to show we know it is a
%. 47.3%. 47.3% of the
respondents like spinach. 145/275
How many men like spinach? 45
What percent of the men like spinach? The base of the
calculation is the number of men. The numerator
is the number of men who like spinach.
45/110 40.9% of the men
like spinach. This is the "column percent" for the cell
What percent of those who like spinach are women? The base is the
number who like spinach. The numerator is the number of women who
like spinach. 85/130 =/6538 = 65.4% This is the
"row percent" for the cell
What percent of the respondents are men who don't like
spinach? The denominator is 275. The numerator is men
who like spinach, 65. 65/275 =
23.6% This is the "total percent" for the cell
What percent of the respondents are men? 110/275 =
40.0%
What percent of the respondents are women? 165/275 = 60.0%
Men Women
Like
40.9% 51.5%
Don't
59.1% 48.5%
Total
100% 100%
N =
(110) (165)
Finally, we can make a finished percentage table with the independent
variable as the base of the percents.
We did this chart before,
but it is relevant to this week as well:
Age at Marriage and Likelihood of Ever Being Divorced by Income at Age
Sixteen
Income at
Age
16
Below
Average
Average
Above Average
Age at
Marriage
<20
20+
<20
20+
<20 20+
Ever Divorced?
Yes
41.5%
28.3%
36.9%
18.6%
34.3% 19.9%
No
58.5%
71.7%
63.1%
81.4%
65.7% 80.1%
Total
100%
100%
100%
100%
100% 100%
N
=
(270)
(520)
(417)
(859)
(99) (297)
p
=
.000
.000
.000
People who marry before age 20 are more likely to have experienced a
divorce or separation, regardless of their family income when they were
16 years old.