Download Descriptive and inferential statistics

Statistics
Review: Scientific Method
1. Observe something
2. Speculated why it is so and form hypothesis
3. Test hypothesis by getting data
4. Analyze data (using statistics)
Statistics
Is the word glistening used more often in
one register (as shown in COCA) than
another?
SECTION
SPOKEN
FICTION
MAGAZINE
NEWSPAPER
ACADEMIC
PER MIL
0.4
12.0
2.8
2.1
0.6
SIZE (MW)
76.6
69.6
78.1
73.4
73.0
FREQ
32
833
219
156
43
How much different do these frequencies have to be before we can say they are
different? Stats tell you.
Review: P value
Researchers have agreed that if the chance that the
difference between two groups is greater than a certain
percentage, then we will consider the difference to be
statistically significant.
A significant difference is better than one in twenty of
happening by chance (p < .05). The opposite of
significance is random chance.
Review: Types of data
1. Categorical: sex, race, national origin, native speaker, how
often you choose one thing over another, how often a word occurs
in one register versus another
2. Continuous:
height, weight, age, scores on a language test,
IQ, working memory span
3. Ordinal: No fixed interval (first, second, third place in a race)—
what order people choose their favorite dialect
Review: Variables
Dependent: what the test measures
Independent: what you think may influence
the dependent
Experiment asks how independent variables
effect the dependent variable
1. Categorical
100
92
90
90
80
75
70
60
61
59
51
50
41
40
32
30
20
8
10
0
Australia
England
India
Ireland
Kenya
New York
Scotland
South Africa Southern US
Correct dialect identification by American English speakers
2. Continuous
5
Utah
Non-Utahs
4
3
2
1
0
Utah
West NonWestern
ers
3. Ordinal (Rank Order)
Coupland & Bishop, 2007
Two types of statistics
1. Descriptive (used to describe data)
a. average (mean)
b. percentile
c. highest and lowest scores
2. Inferential (used to test hypothesis)
a.
b.
c.
d.
chi-square
t-tests/ANOVA
correlations
regression
Descriptive vs. Inferential
Descriptive: Class A had 75% average on
test and Class B had 81%
You can't conclude that B is better than A.
Inferential: Statistical analysis (t-test) shows
that the grades in B are significantly higher
than in A.
1. Descriptive Statistics
These are the types of statistics you are familiar
with—showing means, percentages, quartiles,
usually through bars, pie charts, and graphs
15
12
9
6
3
0
spoken
fiction
mag
news
academic
2. Inferential Statistics
a.
b.
c.
d.
Chi square
ANOVA/t-test
Correlations (rank order correlations)
Logistic regression
2. Inferential Statistics
For each type of statistics we need to know
1.
2.
3.
Statistical value (R value, chi square
value, F statistic, t statistic)
Probability value (p value)
Degrees of Freedom (df)